dlpoly: run and test Argon script

Run and test the [Argon-a-to-z script for DLPOLY](https://github.com/MDMCproject/MDMCv0.2_pilot/blob/master/examples/argon-dlp.py) and check if it produces output consistent with that from the LAMMPS equivalent (e.g. see the [Jupyter notebook here](https://github.com/MDMCproject/MDMCv0.2_pilot/blob/master/doc/tutorials/Argon-a-to-z.ipynb)). This includes:
- `S(Q,w)` is consistent for equal/comparable (hyper-)parameters
- the figure of merit is comparable equal/comparable (hyper-)parameters

This issue should be done after the DLPOLY units have been checked:https://github.com/MDMCproject/MDMCv0.2_pilot/issues/926