Settings : NavigationBar Customization

Contains:

- Settings side to customize the navigation bar buttons.
  Id: I39d9362f1930dc4181d20ff95077b4c290f6907e

- Settings : NavigationBar Customization
  Settings side to customize the navigation bar buttons.
  Id: Ibd51fbca96d5f0d5e75c7bd74dc5ec62ed1d969d

- Settings: Fix NavBar lock button when resetting default
  When the NavBar is reset to defaults while in edit mode, lock icon should
  re-lock
  Id: I876725046e380ebb7da774ae412ce2b68f5310f8

- And a few small fixes

- Add support for navbar editing on tablets

- Add npe check

Change-Id: Ic77ca21d976015a1f4b4e10cab27fa35760035da

Conflicts:
	res/values/strings.xml
	res/xml/system_settings.xml
	src/com/android/settings/cyanogenmod/SystemSettings.java