autodoc plugin for sphinx

[minrk]

Perhaps related to #131, we should consider an extension to sphinx autodoc that would let you include trait info, such as types and help strings, in autodoc output.

This doesn't have to start in this repo, it can be a standalone extension, but I think it would be useful for things like generating good docs on what's configurable in a project.

[rmorshea]

@minrk, so far #131 pulls help text from TraitType.info(), lists the initial metadata, and shows a trait's associated event handlers. Is there more information that would be good to automatically generate?

[minrk]

I'm mainly thinking of generating a nice rst summary with type info and help strings. The mechanism will probably be similar, but the output will probably need to be a bit different, since it should do things like .. autoattribute::, etc., and indicate whether they are configurable, etc.