Add a full guide detailing the common structure, technical standards, style conventions, and writing guidelines

[CAM-Gerlach]

Issue Description

Currently, we have only a very minimal set of standards, conventions and guidelines in our contributing guide; this proposes adding, likely as a separate document with a few elements from contributing merged in, a comprehensive outline of the common document and file structure, the technical standards to be adhered to, and the style conventions to follow for rst and prose, and guidelines to writing accessable technical documentation. I've written up a copy locally, but it is still in draft form and may still change before #13 is completed, and also needs some polish and clarification for public release. Therefore, I plan to do this as one of the first tasks after the initial public release.

Also, as part of this should update PR (and Issue?) templates with "check style guide", and should also add how to create a fork, branch, and submit PR to the contributing guide, and any other build instructions.