Added playlist activity.
Changed music playback to service.
Implemented media controlling by headset media button.
Music stops when headset is disconnected or any other task requires audio focus.
Merge branch 'create-music-player' of github.com:Danguilherme/uMusic into create-music-player

Conflicts:
	AndroidManifest.xml
	src/com/ventura/umusic/music/player/MusicPlayer.java
	src/com/ventura/umusic/ui/music/player/MusicPlayerActivity.java
	src/com/ventura/umusic/ui/music/player/PlaylistActivity.java
	src/com/ventura/umusic/ui/music/player/PlaylistAdapter.java