Battery stats issues: fix jiffy handling, print scan counts.

Issue #19431959: Framework incorrectly assumes that kernel
clock_ticks are 10ms

We now retrieve the time of a jiffy from the kernel, and all CPU
times are now handled in milliseconds.

Issue #19571810: Add per-app breakdown of number of WiFi scans
in batterystats checkin data

Added to the report (the information was already being tracked).

Change-Id: If1702d6b9bcf851704129f1811471e68ed576a5d