rudimentary logging of screen_on and process start/crash via logd to

statsd. The numbers should be replaced with protobuf enums and the
format is subject to changes. But this gets it working for now.

Test: flash with new image, statsd should print out events. toggle
screen on from off state will add a log entry

Change-Id: I733e249965689f00597232c0e3eccfd26e1a958c