add message to perform N1QL request with raw json response

In some use cases, notably when developing a REST backend that could just build N1QL queries and pass the JSON response back to a javascript frontend, being able to perform a N1QL query and not interpret the response but rather return is raw (JSON ByteBuf) can make sense.
A dedicated message can be implemented for this that will just aggregate the response body in the handler and return it. The HTTP status code and message can also be returned.

Note that FTS currently has an approach similar to this (there is no parser and specific response interpretation in the core, although there could be in the future).