Frameworks: add ability to change the color in battery saver mode (1/2)

User complain about the ugly orange....give the user the ability to change the
color in status and navigation bar if battery saver mode is activated.

Especially for you Tylog :D

PS
- move it into the observer...method is called to often to call every time
  the settings value for it.

Change-Id: I48ed2e85c462a2e94770b2bc1ad75b1ca40f2304