Fix /rdf/ responses and use public_uri from etc/default.ini in rdf/webservice.*
Do not use a hardcoded uri for /rdf/webservice#.

Development servers can now have something like
http://localhost:8002/rdf/webservice# during development, while
keeping something like https://example.com/rdf/webservice# as the
official uri in etc/site.ttl.
flake8 fixes.
Add the hydra entrypoint at /ws/.