Preparations for dismiss all button for Lockscreen notifications

This is a part of "Recents: Clear all button for recent apps." from PA

Original Change-Id: I93d1d4cb34325190b03ae3a0d40e1bc170c92d91

Change-Id: I4fe2f132ac7bbde0c21cb1ddbb10f49c877e0aed
Lockscreen Notifications: dismiss all button, improve animations, cleanup

Conflicts:
	packages/Keyguard/src/com/android/keyguard/NotificationHostView.java
	packages/Keyguard/src/com/android/keyguard/NotificationViewManager.java
	packages/SystemUI/res/layout/navigation_bar.xml
	packages/SystemUI/src/com/android/systemui/statusbar/phone/NavigationBarView.java

Change-Id: I1840ee2ea15d57d562c15d9924ce860b7ec51b97