webserver: add id and url fields to zones

'url': Per the specification.
'id': web-safe lookup key for zones. Not implemented correctly yet,
and the specification is lacking a description.
webserver: fix zone list to not have a root element

Per the specification.
webserver: add GET /servers/localhost/zones/<id>
webserver: add (failing) test: zone create with slash
ws.cc: indent fix
webserver: make unsigned zones work with dnssec=on
webserver: implement POST /../zones/<id>

Unify master/masters to masters on the way.
webserver: document that URL registration order matters

While at it, cleanup ordering of routes. Doesn't actually matter for
the existing routes.
yahttp: fix empty body for !POST requests
webserver: send 422 when request was incomplete
webserver: add DELETE /../zones/<id>
webserver: drop codepaths from /jsonstat
webserver: implement statistics, fix config

Per the specification.
webserver: add PATCH /../zones/<id>/rrset

(And drop the old /jsonstat code for this.)
regression-tests.api: Refactor zone tests

Adds a create_zone helper method, to keep down the repetition.
Merge pull request #1248 from zeha/f/ws

Auth. Webserver Updates