ENH: reduce communication argList at startup (#3142)

- replace point-to-point transmission of the argList args/options with
  a broadcast. This is sufficient for most cases (without distributed
  roots).

  For "normal" cases (non-distributed roots) this will replace the
  nProcs-1 messages with a single broadcast.

- for cases with distributed roots, distinguish between a single,
  identical root and different roots.  An identical root can also be
  subsequently handled with a broadcast. Different roots will still
  require individual point-to-point communication.

  For cases with distributed roots, it will add the overhead of an
  additional broadcast.