Web UI serves NS static assets and NS api on port 8091.

Instead of mushing couchDB REST api and NS REST api into one port
(8077), the NS REST api (and NS static assets) are now served by
default via -rest-ns=:8091 cmd-line parameter.

NS static assets are from couchbase/ns-server: 2.1r-133-gde0aa5a
REST ns api /versions implemented.
Provide couchApiBase on separate port.
More progress towards subset of NS web UI.
REST ns api implement thisNode flag.
REST ns api for LocalRandomKeyURI.
Repeated mux path for couchDbGetDb().