Add BatteryStatusFeatureProvider

This allows the battery header status line to be overridden.

Bug: 150239363
Test: implemented provider and changed status line text
Signed-off-by: Jeffrey Carlyle <jcarlyle@google.com>
Change-Id: I05bedbee641f087de5ee1b25a00724ce2de51f87
Merged-In: I05bedbee641f087de5ee1b25a00724ce2de51f87