- accept plain lists (space or comma separated) as well as the
  traditional OpenFOAM lists. This simplifies argument handling
  with job scripts.

  For example,
     simpleFoam -ioRanks 0,4,8 ...
  vs
     simpleFoam -ioRanks '(0 4 8)'  ...

  It is also possible to select the IO ranks on a per-host basis:

     simpleFoam -ioRanks host  ...

- expose rank/subrank handling as static fileOperation methods