UPDATE: adjust structure for new python.quantecon.org bucket

[mmcky]

This PR makes adjustments for the new python.quantecon.org s3 bucket structure.

Tasks:

• add new landing page
• add about_lectures.rst page
• populate about_lectures.rst (@jstac)
• adopt a new custom python theme. (@DrDrij working on python-html.tpl)
• updates to Makefile for new theme
• migrate new theme to private theme and adopt default editing theme in this repo

Cleaning:

• @DrDrij to clean up the theme folder of any unused assets.

[mmcky]

@DrDrij in the new template it would be nice if we could have an easy to enable announcements panel. Perhaps under the breadcrumbs that we could post short term information.

[mmcky]

• @DrDrij we will need to address these on this branch. I am happy to make the changes when you're ok with a pull/push

/home/ubuntu/repos/lecture-source-py/source/rst/404.rst:3: WARNING: Title overline too short.

**********
Page Not Found
**********
looking for now-outdated files... none found
pickling environment... done
checking consistency... /home/ubuntu/repos/lecture-source-py/source/rst/404.rst: WARNING: document isn't included in any toctree
/home/ubuntu/repos/lecture-source-py/source/rst/search.rst: WARNING: document isn't included in any toctree
/home/ubuntu/repos/lecture-source-py/source/rst/status.rst: WARNING: document isn't included in any toctree

[mmcky]

• pdf construction using make pdf and ipynb_pdf_constructor doesn't seem to be working for this branch. (@mmcky) and gets stuck on about_lectures.

This is now working. Lecture need to have a .. contents toc for ipynb_pdf_constructor to not fail.

[mmcky]

Fix the next round of sphinx warnings

/home/ubuntu/repos/lecture-source-py/source/rst/index_toc.rst:61: WARNING: Explicit markup ends without a blank line; unexpected unindent.
looking for now-outdated files... none found
pickling environment... done
checking consistency... done
preparing documents... done
writing output... [100%] zreferences                                                                                                                                                                                                          
/home/ubuntu/repos/lecture-source-py/source/rst/index.rst:: WARNING: Invalid jupyter kernels. jupyter_kernels: {'python3': {'kernelspec': {'display_name': 'Python', 'language': 'python3', 'name': 'python3'}, 'file_extension': '.py'}}, lang: python3

[mmcky]

User Testing Results:

• execution badge links from status.html page link to py folder context and 404
• execution test badge on index pages should show total execution stats (% passing) on status.html and pass/fail on all lecture pages

• @DrDrij should execution badge be right aligned as in the picture above?

• troubleshooting needs to be setup (@mmcky) fa5c28b

• Report Issue needs to be setup (@mmcky) -- investigate if issue template can be used in lecture-source-py. No going to bother with templates

• Add Report Issue link to https://github.com/QuantEcon/lecture-source-py/issues @DrDrij

• there are no breadcrumbs on https://preview.python.quantecon.org/index_toc.html

• Alternative lecture listings for undergrad and grad courses are still linked to py folder context https://preview.python.quantecon.org/py/index_undergrad.html

• homepage meta-title needs fixing (@DrDrij)

• tidy up undergrad and grad index pages

[mmcky]

• pdf construction of 404 halts ipynb_pdf_constructor. @AakashGfude perhaps we should add a simple file filter for these types of documents for ipynb_pdf_constructor

[mmcky]

• @DrDrij would you mind to add in the hide for the following in the theme ([migration] Theme location updates + Other Issues #681)

[DrDrij]

Rock and roll.