Epic: enhance user docs and training

[jcschaff]

Motivation

• Improvement of documentation and user training materials will allow vcell to have a greater impact.

Completion Criteria

• User documentation is up to date.
• Tutorials/Quickstarts are up to date.
• undocumented features are documented.

Tasks

• [x] #186
• [x] #196
• [x] #197
• [x] #198
• [ ] #207
• [ ] #315
• [ ] https://github.com/virtualcell/usermaterials/issues/1
• [ ] https://github.com/virtualcell/usermaterials/issues/2
• [ ] update README.md for vcell-solvers repo (update build instructions and list solvers).

[ACowan0105]

@jcschaff we actually have a "user materials" project that I initiated for the moving boundaries tutorial. However, it is in limbo at the moment. I think it would be good to resurrect and keep that as a separate repository for the future, but I will need some buy in and others who will look at it occassionally as I have such limited time.