Phone: transparent in call widget (optional)

To see the complete contact picture on incomming calls
a lot prefer to have a transparent background. This commit
introduces this feature as optional option.

ChevyCam94:  I omitted his reorganization of the settings options
             but left everything else in tact.

PS3: fixed my previous derps

Change-Id: I826ad4912d0a621fdb611b777681556ea1aea8a1