Revert "Add back navigation ring customization."

This reverts commit ab99452d34b8ce4f73cfa2365422ea0507ce6552.

Conflicts:
	res/values/cm_strings.xml
	res/xml/system_ui_settings.xml
	src/com/android/settings/cyanogenmod/SystemUiSettings.java

Change-Id: I59d18bddd058cf042a990b4cdafaa006b17eec37