- implicitly enabled when timeStampMaster (default) is used
  for the fileModificationChecking

- When running with non-distributed roots (eg, NFS-share) read for
  processor directories on master only and send to sub-processes
  instead individual reads.

- If disabled (old default, or when running with distributed roots),
  uses the regular fileHandler readDir, which may perform readDir
  on each processor. Potentially slow startup times on large systems.

Improvements based on analysis from T.Aoyagi(RIST), A.Azami(RIST)