[Muine] CD sets

[Tamara <foxxygirltamara gmail com>]

We should display the disc number as if it was part of the album title.

For example, currently the Add Album Window displays two copies of
"Van Halen - Right Here, Right Now" which looks rather odd. We should
instead display "Van Halen - Right Here, Right Now (1/2)" or something
similar.

This shouldn't be too hard to add to the code, but what does everyone
think of it?