Various battery info things:

- Now track wake locks in battery history.
- Now track sensors in battery history.
- Some filtering of sensory data.
- Fixes to some data that wasn't cleared when resetting battery stats.
- Print amount discharged since last charge.

And the big part -- keep track of wake locks held per process,
and kill processes that hold wake locks too much while they are in
the background.  This includes information in the battery stats
about the process being killed, which will be available to the
developer if the app is reported.

Change-Id: I97202e94d00aafe0526ba2db74a03212e7539c54