Themes: Make notification list bg themeable

Thanks Thomas Ekelschot :)

Screen of themed resource https://imgur.com/c8t1Zn0

PS2: Add Clark's proposed changes
PS3: Cleanup old color resource in main xml
PS4: Add informative screen

Signed-off-by: Carlo Savignano <stevewatersy@gmail.com>
Change-Id: I8eb4427747c3eb035b416860c3ca47122e45c16f
QuickSettings : Register/unregister cast tile one time

Don't do these operations every time the parent is visible/invisible,
it causes jank.

Repro:

Turn on wifi on a network w/ chromecast
Swipe down quick settings panel really fast

Change-Id: I3dfcd3610abe96e1bfdab06ef3b876ccf5140ceb
QuickSettings : Properly restore lockscreen tile state

The keyguard lock relies on device policy manager service to be active,
currently it fails because it tries to request before its up. Fix that
by registering the request in a receiver

Change-Id: I15e0d980ecf21c8316f4a771e93f4b520c556115

Conflicts:
	packages/SystemUI/src/com/android/systemui/quicksettings/ToggleLockscreenTile.java