b/2296110 Dialog for setting up dock audio.

Reimplemented as a Foreground Service just so it can get on top of the Car Dock App.
Added debounce mechanism to not disconnect immediately after getting a undock event.
Each dock now has its own "Remember setting".
Remember Settings is on by default

Change-Id: I80790bdb7c831e2a642365b92433012191aa70c1