Glossary terms for abbreviations in documentation

[jacobcook1995]

Is your feature request related to a problem? Please describe.
The soil model (and I'm guessing the other models) uses a lot of acronyms, e.g. MAOM for mineral associated organic matter. Having to write out these acronyms every time in docstrings/documentation is tedious, but just writing out the acronyms leads to fairly unreadable documentation.

Describe the solution you'd like
The sphinx extension hoverxref allows us to define a glossary which is then used to generate tooltips explaining terms (and in this case acronyms). I will look into this for the soil model as it is pretty acronym heavy