music/playlist: controls tweak - "select" is main

Limited to music section and playlist (audio + video):
- SELECT to start continuous replay
- PLAY to replay just single track/video
For audio this is essentially a button switch, for playlist video the
preplay screen is lost… (shall it be pushed into scribble menu?)
Make 'PIL/Pillow not installed' item unselectable
Fix xml names - Linux filenames are case sensitive
Merge pull request #3 from iBaa/master

Pull