Quick merge all tracks within an album

[robbevp]

A lot of merges will happen when there is a better audio version/encoding of an album, or one version of a duplicate is deleted.
At the moment a mod+ will have to merge each track manually, while there will often be a very consistent pattern for all tracks. One version of the track will have no audio, and tags will consistently come from the new or old track.

Maybe figure out if we can merge all tracks if there is such a clear pattern and spare the user from clicking 5x per track. This will never work for all situations, and will probably depend on (at least) the tracknumbers matching.