This replaces !40 (closed) .
Standardize file references files during import and export of an ogs6_obj.
File references during import (read_in_prj()) are made always absolute and a conserved during export, except the user specifies to copy the references files into sim_path; then relative file refs are used.
To support python script files, the class prj_python_scripts has been added.
Following files are supported:
*.dat*.gml*.vtu (meshes)*.py (python_script)