Merge changes from topic "starttimemillis-unix" into rvc-dev

* changes:
  Document that ConnectionEvent.startTimeMillis is Unix time
  metrics_pdd_hook: allow committer to specify reason if PDD does not need to be updated
tree: d542d47456ed538cacdd814f36f81b06078202c2
  1. apex/
  2. service/
  3. metrics_pdd_hook.py
  4. PREUPLOAD.cfg