Handle compilations with album artists

[zoomorph]

Compilations are currently detected via having "Various" as the artist name.

Discogs now has named compilations where the complier or mixer is written as the album artist.

There should be an option to detect these and threat them as normal complilations, ie. replace the album artist with CONF.va.

[zoomorph]

Discogs simply does not have the concept of a Compilation = Various Artists anymore.

In foo_discogs 2.0 it can be approximated using a custom formatting script.