Move the connection change callback to its own type

So disconnected activity doesn't have to implement all the unused
callbacks
SqueezePlayer integration

Add posibillity to start the SqueezePlayer PlaybackService.
The service is started as per http://www.squeezeplayer.com/2013/05/start-squeezeplayer-on-startup/

This functionality is enabled by default, if SqueezePlayer is installed,
but the can be disabled via Settings.