Remove org.opendaylight.restconf.nb.rfc8040.rests.utils

org.opendaylight.restconf.nb.rfc8040.rests.utils contains standalone utilities which operate at various levels – mostly dealing with RestconfStrategy without the implication of a full RestconfDataService.

Eliminate individual classes here, replacing them with either RestconfDataServiceImpl integration (where JAX-RS is involved) or RestconfStrategy integration (where it is not).

Success criteria here are:

• org.opendaylight.restconf.nb.rfc8040.rests.utils package is gone
• RestconfDataServiceImpl is a plain HTTP wrapper around RestconfStrategy lookup and invocation
• RestconfStrategy and RestconfTransaction semantics are completely defined around either Netconf or DOMDataBroker