Add new modules to hide details of argparse and mpi4py.
Make description an optional parameter to parse_args.
Clean up multiline comments.
Use saftargs; use print_elapsed_time; clean up long lines.
Use saftargs; use print_mpi_rank and print_elapsed_time; warn if process is redundant;
tidy creation of communicator; clean up long lines.
Use saftmpi to hide details of Py4MPI from MPIsaftmain.
Clean up.