Remove from db on file deletion

[ShaneIsrael]

Right now the observer is only handling adding of additional items. It also needs to remove when it detects media being deleted.

If an episode/movie file is removed, remove it from the database.
if a root series season is deleted. remove the series and corresponding episodes from the database.
if a root series/movie folder is deleted. remove the series/movie from the database and all connected data.