Settings: Add option to always show battery status on lockscreen (2/2)

Based on the feature by burnsra in CM7
Authored by blunden
Tweaked by dvtonder
Change-Id: I1c8c8eef3d0c913c621f735e7d5e395c8768fe76

lockscreen battery status: add off option (1/2)
Change-Id: I06dd1b81826bdb1c1e35b72d99970f97dcad1a34