Library: removed setting libraryMonitoringInitialDone in pref plist
- This is handled in the CoreData MonitoredFolder now
Fix issue where track counts in artist cell are not up to date.
- LibraryAlbums now observe changes to their own track collection
- When there is a change, it informs the parent LibraryArtist that
  'tracks' key changed for the LibraryArtist
- This triggers a new KVO in the LibraryViewArtistCell which re-updates