Introduce NodeJS codegen for Google Cloud Functions. (#4406)

* Another approach: extending NodeJS server to support GCF.

This does not add a new language, but adding some client options
to support Google Cloud Functions (GCF).

* Add URLs for how to deploy the generated code.

Adds the client options help message and the README.md file.

samples/server/petstore/nodejs-google-cloud-functions/controllers/Pet.js

@@ -0,0 +1,39 @@
+'use strict';
+
+var url = require('url');
+
+
+var Pet = require('./PetService');
+
+
+module.exports.addPet = function addPet (req, res, next) {
+  Pet.addPet(req.swagger.params, res, next);
+};
+
+module.exports.deletePet = function deletePet (req, res, next) {
+  Pet.deletePet(req.swagger.params, res, next);
+};
+
+module.exports.findPetsByStatus = function findPetsByStatus (req, res, next) {
+  Pet.findPetsByStatus(req.swagger.params, res, next);
+};
+
+module.exports.findPetsByTags = function findPetsByTags (req, res, next) {
+  Pet.findPetsByTags(req.swagger.params, res, next);
+};
+
+module.exports.getPetById = function getPetById (req, res, next) {
+  Pet.getPetById(req.swagger.params, res, next);
+};
+
+module.exports.updatePet = function updatePet (req, res, next) {
+  Pet.updatePet(req.swagger.params, res, next);
+};
+
+module.exports.updatePetWithForm = function updatePetWithForm (req, res, next) {
+  Pet.updatePetWithForm(req.swagger.params, res, next);
+};
+
+module.exports.uploadFile = function uploadFile (req, res, next) {
+  Pet.uploadFile(req.swagger.params, res, next);
+};