Also take album artists into account when searching. Fixes issue #17.
Also take album artists into account when searching. Fixes issue #17.

elrosti/mopidy-gmusic,jaapz/mopidy-gmusic,Tilley/mopidy-gmusic,jodal/mopidy-gmusic,hechtus/mopidy-gmusic,mopidy/mopidy-gmusic,jaibot/mopidy-gmusic,jeh/mopidy-gmusic