To represent each disc of an album. Discs may have different subtitles
that we want to display (or there may not be a subtitle at all). Casting
a Disc to a string either appends the subtitle to the album name or
returns the album name directly. This is intended to be used by the
ColumnView to display album names
Signed-off-by: Anna Schumaker <Anna@NoWheyCreamery.com>
