IWebServiceConfiguration.createRequest() is not necessary

IWebServiceConfiguration defines createRequest() but I think this is not
strictly necessary. I have a non-Zope WSGI app that has the following
__iter__() in its application object:

    def __iter__(self):
        environ = self.environ
        # Create the request based on the HTTP method used.
        method = environ.get('REQUEST_METHOD', 'GET').upper()
        request = AdminWebServiceRequest(environ['wsgi.input'], environ)
        request.setPublication(AdminWebServicePublication(self))
        # Support post-mortem debugging.
        handle_errors = environ.get('wsgi.handleErrors', True)
        # The request returned by the publisher may in fact be different than
        # the one passed in.
        request = publish(request, handle_errors=handle_errors)
        # Start the WSGI server response.
        response = request.response
        self.start_response(response.getStatusString(), response.getHeaders())
        # Return the result body iterable.
        return iter(response.consumeBodyIter())

The configuration's createRequest() is apparently never called and Gary thinks
it's because lazr.restful is a bit too tied to being running under Zope. If
so, this should be abstracted out of the IWebServiceConfiguration interface.