mod_rest/openapi: Improve organization and navigation Properties roughly sorted by documentation first. GET paths sorted by complexity. Spacing to help with navigation. Some XML stuff that should arguably be a separate commit, but whatever. Tags.

This module helps make BOSH and WebSocket connection endpoints
discoverable via the HTTP method described in
[XEP-0156](https://xmpp.org/extensions/xep-0156.html#http).