SystemUI: Expose heads up.

Signed-off-by: Roman Birg <roman@cyngn.com>
Signed-off-by: Adnan Begovic <adnan@cyngn.com>
Change-Id: I276cb1c80d392b7dbac28e5f553207415b558481

Conflicts:
	core/java/android/provider/Settings.java
	packages/SettingsProvider/res/values/defaults.xml
	packages/SettingsProvider/src/com/android/providers/settings/DatabaseHelper.java
	packages/SystemUI/res/values/arrays.xml
	packages/SystemUI/src/com/android/systemui/statusbar/BaseStatusBar.java
	packages/SystemUI/src/com/android/systemui/statusbar/phone/PhoneStatusBar.java
HeadsUp: Clean up.

Change-Id: I98f445e7a4c92a34a3d9f63e14135e92416875ff

Conflicts:
	packages/SystemUI/res/values/arrays.xml
HeadsUp: Filter out notifications from system uid packages.

    - Settings is very spammy in its notifications, so lets
    just ignore them.

Change-Id: Ic269e8727efb2021d76cccecb9f7e555034d1925