Documentation Documentation Documentation

Here's a first pass at writing some meta-documentation for the documentation system. Documentation.

I'll hold off on merging this until the type stuff actually, you know, works, and open it up for feedback in the meantime. Let me know if there's anything you're unsure about that this doesn't clear up.
I'm just beginning to work on this for Docile. If everything works out right then the 0.3/0.4 documentation transition should be quite smooth.