FB: Heads Up background color && transparency [2/2]

PS: manual rebase

PS: fix my retardedness

PS: fix heads up TRDS background resources

PS: clear content holder background prior to setting TRDS
        drawable so that correct drawable for TRDS state
        is set

PS: revert non-TRDS background to AOSP gray (default
        system notification background color)

PS: clean up some unused code

PS: add capability to set custom heads up text color

Conflicts:
	core/java/android/provider/Settings.java
	packages/SystemUI/src/com/android/systemui/statusbar/BaseStatusBar.java
	packages/SystemUI/src/com/android/systemui/statusbar/phone/PhoneStatusBar.java
Revert "fb: Show heads up at the bottom of the screen (1/2)"

This reverts commit 8a00ecb6a255f25544de6676149c3626642a95ae.

Conflicts:
	packages/SystemUI/src/com/android/systemui/statusbar/notification/HoverLayout.java
	packages/SystemUI/src/com/android/systemui/statusbar/phone/PhoneStatusBar.java