Cleanup and Music Artist and Music Album support

Cleaned up some commented out code, but didn't get as much cleanup does
as I'd like because I realised I should really implement music properly
before removing the old code that does music.
Implemened the well known Music/All Music, Music/Artist and Music/Genre
folders as well as the sub items for those folders which are
MusicAlbumItem, MusicArtistItem and MusicItem