FW: Power Menu customization

All options can now be set to one of the following:
       * Hidden
       * Showing always
       * Showing always except on keyguard if using secure method

P2: Fix issues, set defaults to match stock, and set mDialog = null when dismissed.

Change-Id: I2f84aa45dcebfcf29800a5c06320da61bb4dfe1c
Signed-off-by: Brandon McAnsh <brandon.mcansh@gmail.com>