Revert "remove navigation bar customization"
Good lord this shit gave me a headache.

This reverts commit 4b58b80587a3e562bcc516940c02c8435a417541.

Conflicts:
	packages/SystemUI/src/com/android/systemui/statusbar/phone/NavigationBarTransitions.java
	packages/SystemUI/src/com/android/systemui/statusbar/phone/NavigationBarView.java
	packages/SystemUI/src/com/android/systemui/statusbar/policy/KeyButtonView.java