Separate out schemaless mountpoints

NETCONF is currently abusing DOMMountPoint and especially DOMRpcService to funnel unparsed anyxml nodes through DOM interfaces.

This relies on a historic leniency of DOMRpcResult of allowing other nodes than containers to carry the result.

This is completely wrong, as NETCONF mount points which do not have a schema should not expose a DOMRpcService, but some completely different service, which does not play pretend it conforms to DOMRpcService specification.

Most notable example is that while normal mount points can be interacted with via Binding components, as we can make sense of the payload. schemaless mounts cannot – yet they pretend their services can in fact be a source of normalized data.