Sqlite3 support

[jpmckinney]

Includes #296. Trying to fix #302.

Had to use db.execute instead of db.remove_index due to a bug in South.

Since I can't figure out how to update SQLite on Travis, here are the two failures and one error from my local machine. If these can't be fixed, I can back out the changes to _get_descendants and just get the other changes through in this PR.

======================================================================
ERROR: test_add_section_in_section (speeches.tests.section_tests.SectionSiteTests)
----------------------------------------------------------------------
Traceback (most recent call last):
  File "/Users/james/Sites/shared/pulls/sayit/speeches/tests/section_tests.py", line 182, in test_add_section_in_section
    'title': 'A test subsection'
  File "/Users/james/.virtualenvs/sayit/lib/python2.7/site-packages/django/test/client.py", line 483, in post
    response = super(Client, self).post(path, data=data, content_type=content_type, **extra)
  File "/Users/james/.virtualenvs/sayit/lib/python2.7/site-packages/django/test/client.py", line 302, in post
    return self.request(**r)
  File "/Users/james/.virtualenvs/sayit/lib/python2.7/site-packages/django/test/client.py", line 444, in request
    six.reraise(*exc_info)
  File "/Users/james/.virtualenvs/sayit/lib/python2.7/site-packages/django/core/handlers/base.py", line 112, in get_response
    response = wrapped_callback(request, *callback_args, **callback_kwargs)
  File "/Users/james/.virtualenvs/sayit/lib/python2.7/site-packages/django/views/generic/base.py", line 69, in view
    return self.dispatch(request, *args, **kwargs)
  File "/Users/james/.virtualenvs/sayit/lib/python2.7/site-packages/django/utils/decorators.py", line 29, in _wrapper
    return bound_func(*args, **kwargs)
  File "/Users/james/.virtualenvs/sayit/lib/python2.7/site-packages/instances/views.py", line 20, in _wrapped_view
    return view_func(request, *args, **kwargs)
  File "/Users/james/.virtualenvs/sayit/lib/python2.7/site-packages/django/utils/decorators.py", line 25, in bound_func
    return func(self, *args2, **kwargs2)
  File "/Users/james/.virtualenvs/sayit/lib/python2.7/site-packages/instances/views.py", line 31, in dispatch
    return super(InstanceFormMixin, self).dispatch(*args, **kwargs)
  File "/Users/james/.virtualenvs/sayit/lib/python2.7/site-packages/django/views/generic/base.py", line 87, in dispatch
    return handler(request, *args, **kwargs)
  File "/Users/james/.virtualenvs/sayit/lib/python2.7/site-packages/django/views/generic/edit.py", line 205, in post
    return super(BaseCreateView, self).post(request, *args, **kwargs)
  File "/Users/james/.virtualenvs/sayit/lib/python2.7/site-packages/django/views/generic/edit.py", line 170, in post
    if form.is_valid():
  File "/Users/james/.virtualenvs/sayit/lib/python2.7/site-packages/django/forms/forms.py", line 129, in is_valid
    return self.is_bound and not bool(self.errors)
  File "/Users/james/.virtualenvs/sayit/lib/python2.7/site-packages/django/forms/forms.py", line 121, in errors
    self.full_clean()
  File "/Users/james/.virtualenvs/sayit/lib/python2.7/site-packages/django/forms/forms.py", line 273, in full_clean
    self._clean_fields()
  File "/Users/james/.virtualenvs/sayit/lib/python2.7/site-packages/django/forms/forms.py", line 291, in _clean_fields
    value = getattr(self, 'clean_%s' % name)()
  File "/Users/james/Sites/shared/pulls/sayit/speeches/forms.py", line 364, in clean_parent
    descendant_ids = [ d.id for d in self.instance.get_descendants ]
  File "/Users/james/Sites/shared/pulls/sayit/speeches/models.py", line 55, in __get__
    result = self.method(inst)
  File "/Users/james/Sites/shared/pulls/sayit/speeches/models.py", line 316, in get_descendants
    return self._get_descendants_by_speech()
  File "/Users/james/Sites/shared/pulls/sayit/speeches/models.py", line 319, in _get_descendants_by_speech
    dqs = self._get_descendants(include_min=True, **kwargs)
  File "/Users/james/Sites/shared/pulls/sayit/speeches/models.py", line 205, in _get_descendants
    s = s[1:]
  File "/Users/james/.virtualenvs/sayit/lib/python2.7/site-packages/django/db/models/query.py", line 1456, in __getitem__
    return list(self)[k]
  File "/Users/james/.virtualenvs/sayit/lib/python2.7/site-packages/django/db/models/query.py", line 1402, in __iter__
    for pos, column in enumerate(self.columns):
  File "/Users/james/.virtualenvs/sayit/lib/python2.7/site-packages/django/db/models/query.py", line 1479, in columns
    self._columns = self.query.get_columns()
  File "/Users/james/.virtualenvs/sayit/lib/python2.7/site-packages/django/db/models/sql/query.py", line 68, in get_columns
    for column_meta in self.cursor.description]
TypeError: 'NoneType' object is not iterable
-------------------- >> begin captured logging << --------------------
django.request: ERROR: Internal Server Error: /sections/add
Traceback (most recent call last):
  File "/Users/james/.virtualenvs/sayit/lib/python2.7/site-packages/django/core/handlers/base.py", line 112, in get_response
    response = wrapped_callback(request, *callback_args, **callback_kwargs)
  File "/Users/james/.virtualenvs/sayit/lib/python2.7/site-packages/django/views/generic/base.py", line 69, in view
    return self.dispatch(request, *args, **kwargs)
  File "/Users/james/.virtualenvs/sayit/lib/python2.7/site-packages/django/utils/decorators.py", line 29, in _wrapper
    return bound_func(*args, **kwargs)
  File "/Users/james/.virtualenvs/sayit/lib/python2.7/site-packages/instances/views.py", line 20, in _wrapped_view
    return view_func(request, *args, **kwargs)
  File "/Users/james/.virtualenvs/sayit/lib/python2.7/site-packages/django/utils/decorators.py", line 25, in bound_func
    return func(self, *args2, **kwargs2)
  File "/Users/james/.virtualenvs/sayit/lib/python2.7/site-packages/instances/views.py", line 31, in dispatch
    return super(InstanceFormMixin, self).dispatch(*args, **kwargs)
  File "/Users/james/.virtualenvs/sayit/lib/python2.7/site-packages/django/views/generic/base.py", line 87, in dispatch
    return handler(request, *args, **kwargs)
  File "/Users/james/.virtualenvs/sayit/lib/python2.7/site-packages/django/views/generic/edit.py", line 205, in post
    return super(BaseCreateView, self).post(request, *args, **kwargs)
  File "/Users/james/.virtualenvs/sayit/lib/python2.7/site-packages/django/views/generic/edit.py", line 170, in post
    if form.is_valid():
  File "/Users/james/.virtualenvs/sayit/lib/python2.7/site-packages/django/forms/forms.py", line 129, in is_valid
    return self.is_bound and not bool(self.errors)
  File "/Users/james/.virtualenvs/sayit/lib/python2.7/site-packages/django/forms/forms.py", line 121, in errors
    self.full_clean()
  File "/Users/james/.virtualenvs/sayit/lib/python2.7/site-packages/django/forms/forms.py", line 273, in full_clean
    self._clean_fields()
  File "/Users/james/.virtualenvs/sayit/lib/python2.7/site-packages/django/forms/forms.py", line 291, in _clean_fields
    value = getattr(self, 'clean_%s' % name)()
  File "/Users/james/Sites/shared/pulls/sayit/speeches/forms.py", line 364, in clean_parent
    descendant_ids = [ d.id for d in self.instance.get_descendants ]
  File "/Users/james/Sites/shared/pulls/sayit/speeches/models.py", line 55, in __get__
    result = self.method(inst)
  File "/Users/james/Sites/shared/pulls/sayit/speeches/models.py", line 316, in get_descendants
    return self._get_descendants_by_speech()
  File "/Users/james/Sites/shared/pulls/sayit/speeches/models.py", line 319, in _get_descendants_by_speech
    dqs = self._get_descendants(include_min=True, **kwargs)
  File "/Users/james/Sites/shared/pulls/sayit/speeches/models.py", line 205, in _get_descendants
    s = s[1:]
  File "/Users/james/.virtualenvs/sayit/lib/python2.7/site-packages/django/db/models/query.py", line 1456, in __getitem__
    return list(self)[k]
  File "/Users/james/.virtualenvs/sayit/lib/python2.7/site-packages/django/db/models/query.py", line 1402, in __iter__
    for pos, column in enumerate(self.columns):
  File "/Users/james/.virtualenvs/sayit/lib/python2.7/site-packages/django/db/models/query.py", line 1479, in columns
    self._columns = self.query.get_columns()
  File "/Users/james/.virtualenvs/sayit/lib/python2.7/site-packages/django/db/models/sql/query.py", line 68, in get_columns
    for column_meta in self.cursor.description]
TypeError: 'NoneType' object is not iterable
--------------------- >> end captured logging << ---------------------

======================================================================
FAIL: test_section_creation (speeches.tests.section_tests.SectionModelTests)
----------------------------------------------------------------------
Traceback (most recent call last):
  File "/Users/james/Sites/shared/pulls/sayit/speeches/tests/section_tests.py", line 88, in test_section_creation
    self.assertEqual(children, [ 'Monday 25th March', 'Oral Answers to Questions - Silly Walks', 'Bill on Silly Walks', 'Friday 29th March', 'Fixed Easter Bill', 'New Clause 1', 'Clause 1', 'Z Clause' ])
AssertionError: Lists differ: [u'Monday 25th March', u'Oral ... != ['Monday 25th March', 'Oral An...

First differing element 5:
Clause 1
New Clause 1

- [u'Monday 25th March',
?  -

+ ['Monday 25th March',
-  u'Oral Answers to Questions - Silly Walks',
?  -

+  'Oral Answers to Questions - Silly Walks',
-  u'Bill on Silly Walks',
?  -

+  'Bill on Silly Walks',
-  u'Friday 29th March',
?  -

+  'Friday 29th March',
-  u'Fixed Easter Bill',
?  -

+  'Fixed Easter Bill',
-  u'Clause 1',
-  u'New Clause 1',
?  -

+  'New Clause 1',
+  'Clause 1',
-  u'Z Clause']
?  -

+  'Z Clause']

======================================================================
FAIL: test_add_speech_metadata_in_section (speeches.tests.speech_tests.SpeechTests)
----------------------------------------------------------------------
Traceback (most recent call last):
  File "/Users/james/Sites/shared/pulls/sayit/speeches/tests/speech_tests.py", line 214, in test_add_speech_metadata_in_section
    _check_initial(self, resp, section, speakers[2], speech_data)
  File "/Users/james/Sites/shared/pulls/sayit/speeches/tests/speech_tests.py", line 152, in _check_initial_speech_data
    test.assertEqual(initial['speaker'], speaker)
AssertionError: <Speaker: Speaker 1> != <Speaker: Speaker 2>

----------------------------------------------------------------------
Ran 86 tests in 7.915s

FAILED (SKIP=3, errors=1, failures=2)
Destroying test database for alias 'default'...

[dracos]

Taking the core changes of this branch and running on the current codebase, it looks like this also needs a switch in _get_descendants to use MIN( start_date || ' ' || COALESCE(start_time, '00:00:00') ) (and a reparse of speech_min into datetimes after the query) as sqlite doesn't use + for string concatenation.
I don't understand the strange empty cursor.description, perhaps someone else will; the Speech error is to do with fetching the penultimate speech of the current section so is ordering related; and there's a couple of new issues in the thumbnail generation (I assume sqlite does things in a slightly different order). (was issue in my local install)

[jpmckinney]

I re-applied the relevant commits to head, and added a commit based on your comments.

[jpmckinney]

My searches re: cursor don't turn up anything relevant.

[jpmckinney]

FYI, MySQL doesn't have WITH RECURSIVE. There are solutions using stored procedures or user-defined variables. The code would be very different, so probably don't want to support it.