Flip to mute/dismiss call

This patch is based on http://review.cyanogenmod.org/#/c/29894/11
to provide easy mute and dismiss functionality for the phone application.

Available actions:

0: no action
1: mute ringer
2: dismiss call

Patch Set 14: move attachListeners() to a better place to ensure
that it actually gets called.
Patch Set 15: corrected styling issues
Patch Set 16: further corrections
Patch Set 17: remove unused import
Patch Set 18: fix issue when action triggers while facing down
Patch Set 19: detach listener when call is answered
Patch Set 20: move detachListeners() to a more approiprate place

Change-Id: I1895a1ce985a2f393ea890fd13531310af611498