base: fix battery stats

* Fix IBatteryStats.aidl posititions. BatteryService.cpp from hardware sensors uses a position token
from the binder. The dock battery patch broke this order, causing sensor stats to be send to
wakelock stats, causing a breakage in the partial wakelock counter.
* Create a separate dock stats implementation to avoid collision in the internal statics variables
of the normal stats implementation.

Change-Id: I22c92d5941804449668530715bf5381b00164593
JIRA: CYAN-3127
Issue: https://jira.cyanogenmod.org/browse/CYAN-3127
Signed-off-by: Jorge Ruesga <jorge@ruesga.com>