OpenRadioss_GUI : create Menu to set Alternate path to MPI

[OlivierWienholtz]

Today, no path to MPI is set.
User must install IntelMPI for Window or OpenMPI for Linux et set path in its environment prior to use it.
One could have a main menu in the GUI to set the Root directory to MPI to set a new default.

Then this default could be stored in the Json settings file.
for next usages.