- bugfix: have ServiceConnection created only once!
- select the context within the PlayerHolder to start, stop, bind or unbind the service
-> we have to make sure the Service is started AND stopped within the same context
-> so let PlayerHolder be the one to select the context
- remove removeListener() and replace the call with setListener(null)
- Compatibility: use ContextCompat.startForegroundService instead of startService()
48c2c156cb