Musicbrainz

Updated MusicBrainz commit. This is pretty extensive and pretty much ready for Frodo I think. 

There is a little bit more love I need to give it yet - primarily I need to remove strArtists from the album/song tables as we can now build those in the DB from the album_artists and song_artists.  Also I need to think a little more about how to fix up all the StringUtil::Join(artist, ...) that we have all over the place. What is in here works but will break if e.g. you try and update the artists via JSON-RPC. Since I don't think you can even do that right now I think it's good.

Would be great if folks can start to review it early. I think there might be some FIXME's lurking in here and whitespace and overall feedback on the style would be great.