Add support for `MSSQL`

[RamizSami]

I am using django-dbbackup with sql_server.pyodbc as my database engine because my database is in MSSQL but it is giving the following error:

File "manage.py", line 10, in <module>
    execute_from_command_line(sys.argv)
  File "/home/ramiz/crawler/local/lib/python2.7/site-packages/django/core/management/__init__.py", line 353, in execute_from_command_line
    utility.execute()
  File "/home/ramiz/crawler/local/lib/python2.7/site-packages/django/core/management/__init__.py", line 345, in execute
    self.fetch_command(subcommand).run_from_argv(self.argv)
  File "/home/ramiz/crawler/local/lib/python2.7/site-packages/django/core/management/base.py", line 348, in run_from_argv
    self.execute(*args, **cmd_options)
  File "/home/ramiz/crawler/local/lib/python2.7/site-packages/django/core/management/base.py", line 399, in execute
    output = self.handle(*args, **options)
  File "/home/ramiz/crawler/local/lib/python2.7/site-packages/dbbackup/utils.py", line 96, in wrapper
    func(*args, **kwargs)
  File "/home/ramiz/crawler/local/lib/python2.7/site-packages/dbbackup/management/commands/dbbackup.py", line 57, in handle
    self.dbcommands = DBCommands(database)
  File "/home/ramiz/crawler/local/lib/python2.7/site-packages/dbbackup/dbcommands.py", line 237, in __init__
    self.settings = self._get_settings()
  File "/home/ramiz/crawler/local/lib/python2.7/site-packages/dbbackup/dbcommands.py", line 250, in _get_settings
    raise Exception('Unknown db engine: ' % self.engine)
TypeError: not all arguments converted during string formatting

How do I use dbbackup with this database?

[ZuluPro]

Hello @RamizSami
We currently make a great refactoring of DBBackup code, but MSSQL isn't actually supported.
Personally, I don't have this kind of platform...

Feel free to submit a patch about it.