OK - implemented in the compare() function - now coverinfos are sorted based on whether there is a cover or not.

Issue:  It's slower than setting the text (as I had done before)  I think it's because it's checking if there's a cover for each file.  Maybe we should hold within the coverinfo object whether or not there is a cover (so we only check it once...or whenever we add or remove a cover)

CCMAIL: wheeler@kde.org

svn path=/trunk/kdemultimedia/juk/; revision=361564