Lockscreen Notifications: rewrite add notification logic

There were some problems with notifications getting replaced while the user was currently dragging them.
This commit should fix that by always waiting until animations and user input are finished before replacing a notification view.

Conflicts:
	packages/Keyguard/src/com/android/keyguard/NotificationHostView.java
	packages/Keyguard/src/com/android/keyguard/NotificationViewManager.java