Telephony: Dismissable voicemail notifications

Ported from cm-10.2:
http://review.cyanogenmod.org/#/c/35023

Change-Id: Iccd01210cdd9a43167392fc09debbfc4cb23b6f6
[2/3] Telephony: allow disabling non intrusive incall ui

Change-Id: I4eec37e8f9ec3a7e062b13deac54a844dc277a03