Revert "Add back navigation ring customization."

This reverts commit a4bc6f3e2de14faab0fe756857b2bd74a13e2fab.

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

Change-Id: I21059ccdfb38e07d138dc3f9e5256cd931ddf2e4