2 changes:
  1) Setting rtt had a bug.  When put in a value to set rtt to, would
  add that amount of latency to any packet on that link.  This meant,
  in effect that we were doubling the rtt requested.

  2) Got rid of large latency test and re-named latency_no_rtt to
  latency contention.  (That's what it's really measuring, plus
  updated its rtt to use 2 ms.)
Added an experiment for read only latency.
Minor param updates for dist error test.
Added an experiment for running with coarse lock.
Require a name for read_only output files.
Allows setting period for collecting statistics for switches on floodlight in experiments.  Currently, defaulting to turn off collection.