Add "show all notifications" navbar button

Conflicts:
	packages/SystemUI/res/layout/navigation_bar.xml
	packages/SystemUI/src/com/android/systemui/statusbar/phone/NavigationBarView.java
Lockscreen Notifications: fix show/hide of show all button

& fix endless SystemUI FC when SystemUI is killed

Conflicts:
	packages/SystemUI/src/com/android/systemui/statusbar/phone/NavigationBarView.java
Lockscreen Notifications: fix NPE
Lockscreen Notifications: try to fix occasionally SystemUI FC on boot