Overhaul BatteryController and related code cleanup (2 of 2)

Summary:
Move text label implementation to a ListPreference
Remove unnecessay warning in BatteryBar animate summary

Depends on D439

Change-Id: I2a70c387b35983451fcffc7523e96f3d5094925c

Test Plan: test and merge

Reviewers: synergy

Reviewed By: synergy

Differential Revision: http://review.codefirex.com/D443