How to present user docs and developer docs

[bjones1]

For many applications -- certainly, CodeChat and the CodeChat System -- there will be both user docs and developer docs. What's the best way to structure these? We need some documentation principles added to CodeChat/docs/style_guide.cpp.

Thoughts:

• Have two separate doctree hierarchies. The homepage will always be the user docs.
• Provide links between user and developer docs at similar levels of the hierarchy.
• Define a naming convention: user-file.rst and dev-file.rst?

After defining this, update the actual CodeChat / CodeChat System docs to use this approach.