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.

---
summary: Log a message once per minute
...

This module sends `-- MARK --` to the log once per minute. This may be
useful to give a sense of how busy the server is or see that logging and
timers are still working.