Shorten the derived parameter archfile_time_step to reduce latency

The original value of `archfile_time_step = 200000` was likely driven by
efficiency in the initial ingest.  This has the bad side effect of
making derived parameter values lag behind by up to ~3 days.  Shortening
the value to 10000 will reduce latency to less than 4 hours behind the
main telemetry.
Merge pull request #52 from sot/shorten-dp-time

Shorten the derived parameter archfile_time_step to reduce latency