When dozing, re-enable falsing threshold and log events.

- Reactivate our configured keyguard falsing swipe threshold
  for secure keyguards, but only when dozing.
- Add DozeLog helper to capture/maintain interesting events
  about the doze + unlock process, enabled by default, but
  only on devices that start dozing at least once.
- Dump summary counts + logged events to dumpsys output.
- Pass notification pulse "instance" as an extra to the scheduled
  intent, so we can log accordingly.

Bug:17496795
Change-Id: I7e88f93bfc967bdc06550cf1fe5e74d535edd774