SystemUI: Fix potential NPE

Does already cause issues on some Halo ports to other ROMs.
Might not cause issues on PA (yet), but better safe than sorry.
LN: Some fixes & cleanup

- Fix bug that the notification is launched when a button on it is pressed
- Show new notifications first

Change-Id: I87db92a7ee4eb9329ec1ec69008e612a619d5c91

Conflicts:
	packages/Keyguard/src/com/android/keyguard/NotificationHostView.java
LN: Fix FC on launching hangouts notification

Change-Id: Idf411bd2b4995f0b53767e99597efd98ce0596b3
LN: beautify

Change-Id: I695846412f2b8c910f8a5cf48da2bf6ac42e124e

Conflicts:
	packages/Keyguard/res/layout-land/keyguard_host_view.xml
	packages/Keyguard/res/layout-port/keyguard_host_view.xml
	packages/Keyguard/src/com/android/keyguard/NotificationHostView.java