Adds docstrings to controls and project fields

[alexhroom]

This PR fixes the remainder of #5 by adding descriptions to all of the fields in Project and Controls. This format uses field docstrings which are loaded into the description model field attribute , meaning they can be picked up both by autodoc-pydantic for the documentation and can also be used in the GUI (e.g. for mouseover help text).

[DrPaulSharp]

All looks good, please review the descriptions I've commented on.

Also, what do you want to do regarding docstrings for the models - descriptions of the fields are already present of course, do you want to put them in this format?