Re-enabling Navigation bar transparency (1/2)
- It's been hidden due the hole new SlimRoms nav bar customization implementation

Change-Id: I1eb1dd55e68fd9025d5cca5ca3a462e8a3a453cf

Conflicts:
	core/java/android/provider/Settings.java
	packages/SystemUI/src/com/android/systemui/statusbar/phone/NavigationBarView.java
	packages/SystemUI/src/com/android/systemui/statusbar/phone/PhoneStatusBarView.java