pump events from STv2 db

This requires the introduction of the time_sync.py service.
A trivial HTTP service that allows the POST/GET of timestamps.
This can used between the consumer and stream pipeline processor
to synchronize time when replaying old events (so they don't
expire too prematurely).

Change-Id: Iba61b3b75f68a19869d06a0484d2676dd44fdc60