TODO: Not sure the app could be accepted on the play store without a valid
banner.

This seems to be required on recent Android versions (tested with Android 10).
This is also required for android TV services (cf. next commit).

This is done using Java reflection so that the project doesn't depend on
android compat libs.

Google Play refuses uploads with a lower targetSdkVersion.

add 2 preferences to:
 - enable Wakelock when MPD is running (prevent suspend)
 - run MPD on boot

and display MPD logs

 - <uses-permission> must be before <application>
 - specify allowBackup (default)

- add Settings: Activity to start / stop MPD Service (Main).

- Main is a service that run in foreground with a notification. See
  Service.startForeground documentation for more details.

- Main.Client is used to control the service: start or stop it and also receive
  callbacks when service encounters an error, is killed, is started or is
  stopped.

- Main.start to start the service without any fallback.

The number of MPD installs on Android < 5.0 is negligible, and that
API version introduces lots of useful features for MPD.