Settings: Default the old CM Power widget to OFF

THe Power widget functionality will be replaced by the new QuickSettings
functionality of Android 4.2.  Turn the old CM widget off by default.

Change-Id: I9144130898aff1fb9f882aaf68a3b0873742f3d6
PowerWidgetUtil: Re-enable LTE button.

- Also use Settings.Global.getInt() for PREFERRED_NETWORK_MODE.

Change-Id: I677de6353bf451fe4390ff74f9703b5df3beb39d