[PHP][Symfony] Enhancements (#6615)

* Removed commented code

* Input validation is now supported as strict JSON validation

* [PHP][Symfony] Improve the implementation
Closes #6614

* Generated code is tested to assure it compiles and updated README to dynamically load dependencies via composer

* Updated shell script because shippable tests were failing

samples/server/petstore/php-symfony/SymfonyBundle-php/Tests/AppKernel.php

@@ -0,0 +1,21 @@
+<?php
+
+use Symfony\Component\HttpKernel\Kernel;
+use Symfony\Component\Config\Loader\LoaderInterface;
+
+class AppKernel extends Kernel
+{
+    public function registerBundles()
+    {
+        $bundles = array(
+            new Symfony\Bundle\FrameworkBundle\FrameworkBundle()
+        );
+
+        return $bundles;
+    }
+
+    public function registerContainerConfiguration(LoaderInterface $loader)
+    {
+        $loader->load(__DIR__.'/test_config.yml');
+    }
+}