Gamma parameter and gammaCalc notes

[phockett]

As of 0ae330a (04/12/24) gammaCalc module is working including spin weightings.

TODO:

• Better integration/handling of QNs and labels over functions.
  • Append term lists to DataFrames.
  • Allow for passing to functions.
  • Integration over functions.
  • Control over coherences. This is currently hard-coded. Test case with Kc, Mc single-terms only working, didn't test for other cases as yet
• Test cases.
  • Currently just tested for Xe, J-selected case. (Notes in progress, see https://phockett.github.io/Quantum-Beat_Photoelectron-Imaging_Spectroscopy_of_Xe_in_the_VUV/intro.html)
• Docs
  • Update main docs for spin-included case, see https://epsproc.readthedocs.io/en/3d-afpad-dev/methods/state-resolved_gamma_python_demo_190724.html