NavigationBar: Custom height (1/2)

Patchset 3 : Fix default value derp
Patchset 4 : Fix custom height during landscape

Change-Id: I61aef192ac658f54f86b87d18cce9d7b073004e2

Conflicts:
	core/java/android/provider/Settings.java
	policy/src/com/android/internal/policy/impl/PhoneWindowManager.java