doc/userguide: generate eve documentation

doc/userguide: generate eve documentation

Add EVE documentation for QUIC and Pgsql to their respective sections of
the userguide.

Also add a complete EVE reference as an appendix.

Other protocols can be done, but its a manual process to document in the
schema, then add the glue to pull them into the documentation.

The documentation is generated during "make dist", or if it doesn't
exist, "conf.py" will attempt to generate the eve documentation for
building on Readthedocs.