LockScreen battery: add off option [1/2]

Change-Id: I066089b7e8329a68038fa6b51b10164df5ad4962
Settings: Use meaningful titles for gamma controls

There is good anecdotal evidence that the values we modify relate
to specific modifications (contrast, brightness, saturation and the
like) of the display, this change allows us to define descriptive
headings.

Change-Id: I2935924fd86f13e95b919e7b7c7a0bc931ac50bb