Settings: Slimrecents background color && transparency [1/2]

Allow user to specify background color and transparency level
    for the slimrecents panel.

Change-Id: I8dd2543a3201b36f8c310de0da54f2f91ca474ef

Conflicts:
	res/xml/accessibility_settings.xml
	src/com/android/settings/accessibility/AccessibilitySettings.java