Fix MusicBrainz nomenclature: album → release

In general, "albums" in everyday usage is what on MusicBrainz would be
considered a release group[1] while as far as I can tell, every single
instance of it being used in whipper is referring to a single "edition"
of an album, which is what would be called a "release" in
MusicBrainz terminology[2].

[1] https://musicbrainz.org/doc/Release_Group
[2] https://musicbrainz.org/doc/Release

Signed-off-by: Frederik “Freso” S. Olesen <freso.dk@gmail.com>

whipper/command/cd.py

@@ -51,8 +51,8 @@ and adding the file extension.  Variables exclusive to the track template are:
 Disc files (.cue, .log, .m3u) are named according to the disc template,
 filling in the variables and adding the file extension. Variables for both
 disc and track template are:
- - %A: album artist
- - %S: album sort name
+ - %A: release artist
+ - %S: release sort name
  - %d: disc title
  - %y: release year
  - %r: release type, lowercase