Add new list fields set by MusicBrainz Picard

[jeandeaual]

Add support for:

• albumtypes

  Parse secondary album types, like Parse secondary album types from MusicBrainz beets#2200 but from the file tags directly.

• catalognums

  Releases with multiple CDs sometimes have multiple catalog numbers (for example this release).

• languages

  A work on MusicBrainz can have multiple languages, and by using Use track relationships in Picard they get written to the files.

Until now, the values could be retrieved with a separator for ID3v2.3 tags, but not for Vorbis tags:

>>> f = MediaFile('test.mp3')
>>> f.albumtype
'album/audio drama'
>>> f = MediaFile('test.flac')
>>> f.albumtype
'album'

With this PR:

>>> f.albumtypes
['album', 'audio drama']
>>> f.albumtype
'album'

[sampsyo]

Awesome; thank you for adding these! This looks perfect!!

Do you think you could add a quick changelog entry under a new "v0.10.0" heading here?
https://github.com/beetbox/mediafile/blob/master/docs/index.rst#changelog

[jeandeaual]

Do you think you could add a quick changelog entry under a new "v0.10.0" heading here? https://github.com/beetbox/mediafile/blob/master/docs/index.rst#changelog

Done!

[sampsyo]

Wahoo; looks excellent! Thank you again!