Update the API Overview docs for modern recommendations and options.
Review Request #9380 — Created Nov. 15, 2017 and submitted — Latest diff uploaded
The API Overview docs were getting a bit stale, talking about "future
plans" for XML that are no longer planned, and missing a couple of HTTP
status codes we support.This fixes up some of those docs, making the HTTP listing better,
removing some text, and adding a recommendation around XML.
Built the docs. Checked for build, spelling, and link errors.