Fix MPI executable for local .sh script if jobscripts were written on HPC

[jhnnsnk]

PR #2 hardcoded MPI executable from HPC for local runs which now hinders local reruns of, e.g., plotting steps.
Vice versa is also an issue.
If have nothing against hardcoding the correct executables (as before or putting them into the system parameters) or putting in the .sh scripts that the respective one should be determined at runtime.

Need to check what can be put into systems parameters file (user specific).

[espenhgn]

Can't you simply rewrite the job scripts locally without deleting simulation output folder/files which may be present?