Change gnome-music category from deskutils/ to audio/. Update RMPORTS.

Also fix the installation of org.gnome.Music.gschema.xml by listing it in
the port Makefile instead of in the pkg-plist.


git-svn-id: svn://creme-brulee.marcuscom.com/ports-experimental/trunk@19444 df743ca5-7f9a-e211-a948-0013205c9059