Unifying Cloudy scripts with sps incident scripts

[WillJRoper]

To ensure consistency, and importantly consistent naming and units, this PR introduces the Parser and GridFile to the cloudy scripts.

Currently an open draft to enable collaboration.

Issue Type

• Enhancement

Checklist

• [x] I have read the [CONTRIBUTING.md]()
• [x] I have added docstrings to all methods
• [x] I have added sufficient comments to all lines
• [x] I have made corresponding changes to the documentation
• [x] My changes generate no pep8 errors
• [x] I have added tests that prove my fix is effective or that my feature works
• [x] New and existing unit tests pass locally with my changes

[sophie-newman]

why the hf=None? is that just for testing?

[WillJRoper]

why the hf=None? is that just for testing?

That's literally just so the script with the few changes I had made would make it past the commit checks. I've done very little so far here but opened it in draft so we can work together on it.

[sophie-newman]

I have tested this and everything is looking as expected!

Main changes in this PR:

• Plural axis naming
• Inclusion of units. This is done in a very simple way in lines 132-149 of create_synthesizer_grid for a few example axes (reference_ionisation_parameter, ionisation_parameter, metallicities, ages). If an automatic way could be found, this would be preferred but it is hard to do this from the .yaml file.
• Move grid creation to create_synthesizer_grid rather than create_cloudy_input_grid
• Update parser arguments to use -- rather than -

[WillJRoper]

This looks fine to me. There could be some hidden gremlins but I don't see them. The proof will be in the pudding.

@christopherlovell I can't approve this since I made the original PR.