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/UserService.js

@@ -0,0 +1,100 @@
+'use strict';
+
+exports.createUser = function(args, res, next) {
+  /**
+   * parameters expected in the args:
+  * body (User)
+  **/
+  // no response value expected for this operation
+  res.end();
+}
+
+exports.createUsersWithArrayInput = function(args, res, next) {
+  /**
+   * parameters expected in the args:
+  * body (List)
+  **/
+  // no response value expected for this operation
+  res.end();
+}
+
+exports.createUsersWithListInput = function(args, res, next) {
+  /**
+   * parameters expected in the args:
+  * body (List)
+  **/
+  // no response value expected for this operation
+  res.end();
+}
+
+exports.deleteUser = function(args, res, next) {
+  /**
+   * parameters expected in the args:
+  * username (String)
+  **/
+  // no response value expected for this operation
+  res.end();
+}
+
+exports.getUserByName = function(args, res, next) {
+  /**
+   * parameters expected in the args:
+  * username (String)
+  **/
+    var examples = {};
+  examples['application/json'] = {
+  "firstName" : "aeiou",
+  "lastName" : "aeiou",
+  "password" : "aeiou",
+  "userStatus" : 123,
+  "phone" : "aeiou",
+  "id" : 123456789,
+  "email" : "aeiou",
+  "username" : "aeiou"
+};
+  if(Object.keys(examples).length > 0) {
+    res.setHeader('Content-Type', 'application/json');
+    res.end(JSON.stringify(examples[Object.keys(examples)[0]] || {}, null, 2));
+  }
+  else {
+    res.end();
+  }
+  
+}
+
+exports.loginUser = function(args, res, next) {
+  /**
+   * parameters expected in the args:
+  * username (String)
+  * password (String)
+  **/
+    var examples = {};
+  examples['application/json'] = "aeiou";
+  if(Object.keys(examples).length > 0) {
+    res.setHeader('Content-Type', 'application/json');
+    res.end(JSON.stringify(examples[Object.keys(examples)[0]] || {}, null, 2));
+  }
+  else {
+    res.end();
+  }
+  
+}
+
+exports.logoutUser = function(args, res, next) {
+  /**
+   * parameters expected in the args:
+  **/
+  // no response value expected for this operation
+  res.end();
+}
+
+exports.updateUser = function(args, res, next) {
+  /**
+   * parameters expected in the args:
+  * username (String)
+  * body (User)
+  **/
+  // no response value expected for this operation
+  res.end();
+}
+