Prototype better code comments and developer documentation

[darrenrichmond]

Most of the people who come to CfD want, to some extent, tweak the code of the applications we build. But many times they face a huge cognitive barrier because the applications are built on many complicated tools and libraries. This effort shows one way we can provide a mechanism to allow developers just coming to the app to understand enough to help.

The basic idea is to provide a new .md file, linked from the main README.md, that provides full text descriptions of how the system (or a subsystem, such as state transition) is architected, the tools used, justification, helpful links to external resources recommended to get up to speed on tools and libraries used, and an overview of which files are key to understand to "get" that subsystem. Then, in the code, provide comments that are specific to the actual code commented, and refer the user to the .md documentation for further context.

TODO: We should also add unit and automated regression tests to the system to further assist validation and increase understanding and confidence. Once written (each, not once all done, since we will never be all done), they should be referenced and explained in the documentation and comments.