HALO new vertical gestures (NOT READY FOR RELEASE)

itroduces step gestures
-- Clear all notifications
-- Clear current notification
(*)
-- Hide HALO
-- Silence HALO until woken

Patch Set 2: Add updated mdpi/hdpi drawables

Change-Id: I4b5bb7ec612dc0eb1d95e970348b15fba1d79df0