Library schema version 2

* Add fields for musicbrainz album and track ids.
* Reference database by schema version.
Rewrite scanner to use standard library

* Add command line options
* Remove custom library and types
* Use logging module rather than print statements
* Disable bitrate, channels and codec logic
* Update library with musicbrainz-trackid and musicbrainz-albumid
* Remove filesystem walking logic, update_library.py should be called to
  populate the library instead
* Indicate progress and commit changes every 100 tracks
Add album mode

* Don't delete missing tracks, we have clean_library.py for this
* Add album mode algorithm to allow play throughs of whole albums
  * Requires library schema v2
* Add command line option (--album) and keypress (a) for controlling album mode
* Add album mode indicator to title bar
* Add increased debug logging
* Add switch for debug logging
* Move logger setup to __main__