SystemUI: Separate system bar BGs for themes

This commit separates the navigation bar background colors from the
status bar background colors which allows more modular theme-ability.
Backwards compatibility for the old system bar values is still
preserved, but the new values are to be prioritized.

Thanks to Arz Bhatia for the suggestion.

Change-Id: Ibe579d16ea35ca5bdcfe9f98143c3f91cd24900f

Conflicts:
	packages/SystemUI/res/values/cm_colors.xml
	packages/SystemUI/src/com/android/systemui/statusbar/phone/BarTransitions.java
Framework: Make the dialog divider color themeable

The holo blue color might not be suitable for some themes. This commit
swaps out the background of all titleDivider elements to use another
resource. This has no difference from the perspective of the user of a
"stock" build but this is huge for theme users.

Thanks to Arz Bhatia for the suggestion.

Change-Id: Icb917220accac3ad38770067120a7b1be894961a

Conflicts:
	core/res/res/layout/dialog_custom_title_holo.xml
	core/res/res/layout/dialog_title_holo.xml
	core/res/res/layout/dialog_title_icons_holo.xml

Conflicts:
	core/res/res/layout/alert_dialog_holo_dark.xml