Patch: Ignore "The" when sorting, persist maximized state, tweak for mp4 tag reading

[Dan O'Reilly]

Attached is a patch that does the following:
1) Adds a keyword argument to the list_tag method in trackdb.py that will ignore "The " at the beginning of a string when sorting. The new argument is used in the collection panel.

2) Brings back the mainw_maximized setting from 0.2, so that the maximized state is persisted between Exaile restarts.

3) Brings back the _set_tag and _get_tag methods for the .mp4 file type, so that track numbers saved in the x/y format (i.e. 4/12) are displayed correctly. They were getting treated as two separate track numbers previously.

[Dan O'Reilly (oreilldf)]

Resubmitting the patch to make sure it applies correctly with the latest rev...

[reacocard (reacocard)]

committed r1740