Python improvements

[LecrisUT]

I am gathering up a few tasks that should be done to modernize the python libraries used

• Use pathlib.Path instead of os.path
• Use the json schema instead of manual check_directives
• Enable mypy checks Type hints #203
• Fix the cli entry-point and test_suite Use Click for cli #205
  The tests should call the executable directly and parse the stdout/stderr
  The cli could use some more standard cli libraries. click is a good option because it also generates appropriate man pages