Draft implementation of a battery status indicator

Signed-off-by: Simon Busch <morphis@gravedo.de>
StatusBar: complete status bar layout with static app menu, system menu, and a battery indicator.

Signed-off-by: Christophe Chapuis <chris.chapuis@gmail.com>
StatusBar: better layout, and nicer animation on the fadeout of an indicator

Signed-off-by: Christophe Chapuis <chris.chapuis@gmail.com>