Move the WebAPIResource documentation into its own guide.

Review Request #7594 — Created Aug. 16, 2015 and submitted — Latest diff uploaded

Information

Djblets
release-0.9.x

Reviewers

WebAPIResource's docs were generating a large number of errors during
doc build time, mostly due to the fact that class documentation can't
have sections.

Rather than work around that, the overview of all the capabilities of
WebAPIResource have been moved into a Writing API Resources guide.
I've added missing links and fixed up typos as part of this.

Built the docs and read through it. The links were all correct, and
the formatting was fine.