Group albums by album name, not album_id. An album to mythmusic uses the artist > album hierachy, but for albums which have multiple artists this means we have multiple entries in the album table. It's a failing in the way we arrange the data internally, but it's better to have just one entry per album in the upnp output than 10-15 for each artist in a compilation.
Re-enable Artist and Genre groupings for upnp
Add support for music album artwork to upnp.