#11 Add disc # to ID3 album name

[Erhhung Yuan]

When ID3 tags are written to MP3 files that are a part of
a multi-disc album, there's no way to distinguish which
disc a track belongs to because the album title, as
stored in the JukeDaddy, isn't labelled like "(Disc 1)"
and there will be 2 or more files with track #1 having the
same album name. So when writing ID3 album names, if
the file comes from an album with more than one disc,
then append " (Disc n)" after the album name, or " (Disc
n: title)" when disc title support is implemented and non-
empty.