Effem: Add wiredheadset / loudspeaker option for output

v2: remove unused stuff, add constants for output, various minor
corrections, german translation

Change-Id: Ifeed783f5c216dbfd85b3e3ab6cfcd9a99001d90
Audio focus handling

Request and handle audio focus. This is especially important to mute
audio while in a call.
Fix activity stop/start interaction in some cases