Statsd can pull kernel wakelock data

When statsd is told that it is time to poll data, it asks
StatsCompanionService to pull kernel wakelock data, receives the result
(as a string), and outputs it to screen.

Still to do:
1. don't use a string; use a parcel instead
2. don't output it to screen; do something useful instead
3. do more than just kernel wakelocks
4. pull data on demand, in addition to just on periodic pulling

Test: added setPollingAlarms to statsd.main and confirmed that kernel
wakelock information was written to screen
Change-Id: I35f5164420699dea1a00c9e530b938904f1d3055