Fix conflict between mate-media and gnome-media.
Fix middle mouse click on applet.

Obtained from: Upstream
Make sure applets have the mate prefix to fix conflict with gnome-applets.
Not used to git wierdness yet, part 2 of fix conflict with gnome-applets.
Fix conflict with gnome-control-center.
Merge branch 'master' of https://github.com/jlmess77/mate-ports