[MainWindow] Accept content type "Music" as well
[MainWindow] Accept content type "Music" as well

MediaObject2 spec has been changed so "audio.music" type is now
"music". We should try to play both types.

Fixes #8. Note that actual fixes need to happen on dleyna-server
side: This just makes dleyna-control accept all legal values of
"Type".

Signed-off-by: Jussi Kukkonen <589e25658b1bfd3646cd0c60eea9e9594b5e0b5b@intel.com>

01org/dleyna-control,jku/dleyna-control,rmerlino/dleyna-control,lferrandis/dleyna-control