This commit removes `launcher.py` and `launch_expe.py` as they are
redundant with the console scripts defined in `setup.py`.

Namely, `launcher.py` is installed as `pybatsim` and `launch_expe.py` is
installed as `pybatsim-experiment`.

These are not hardlinks but kind of particular refcounters

That was causing a return value of 1 in some cases

The function register_job now returns the Job that was created