Telephony: Dismissable voicemail notifications

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

Change-Id: Iccd01210cdd9a43167392fc09debbfc4cb23b6f6
Merge pull request #2 from CyanogenMod/cm-11.0

Telephony: Dismissable voicemail notifications