Fetch MusicBrainz track disambiguation field

[SimonHova]

I download a lot of singletons, and I use the track disambiguation notes frequently. I saw that Beets has a way to note the album disambig, but not the track disambig. Can this be inserted into a future release? This way, my beets.yaml config could look something like this:

paths: default: $albumartist_sort/[$year] $album/$track. $artist- $title comp: Various Artists/[$year] $album/$track. $artist- $title singleton: $artist_sort/$artist- $title [$trackdisambig]

[sampsyo]

Yes, sounds like a very reasonable addition.