fb: Incoming Call in Background (3/3)

Patch ported from 4.2 which was done by our lovely HCP. A
very popular one so we bring it back and adapt it to 4.4

Allows user to set that Incoming Call UI will remain in background
if screen is on. Instead, a notification is added to StatusBar, which
can be used to bring up the Incoming Call UI. Ringtone and vibration
still occur as per system settings.

This has the same effect as apps marked as "immersive". It prevents
the incoming call from backgrounding the current activity.

Change-Id: I8960ccc453c47d2db38af350b04018e092ef5756
Revert "Runtime toggle of navbar"

This reverts commit b6a1eb3bd5438906f06a076a7c29d97376638496.

Change-Id: I667cbc14f3406e0b87f3b594988d0acab91a9327
Navigation bar dimensions (1/2)

- Change height when in portrait
- Change width when in landscape
- Option to enable or disable nav bar

This is partially ported from SlimRoms
Thanks to @kufikugel

Change-Id: Ic2bfb32684c3d74062d123266db1516e09d92fb6