Lockscreen notifications: Add "show all notifications" navbar button

Change-Id: I0cd5b13e5644de36d24d4d693838bd7080f55412

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

Signed-off-by: siracuervo <fl.siracusa@outlook.com.ar>

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