Add new default alias: "php_cache" (#61)

* Change default alias to "php_cache"

* Also keep the old alias

Author: Nyholm

src/DependencyInjection/CacheAdapterExtension.php

@@ -62,6 +62,7 @@ public function load(array $configs, ContainerBuilder $container)
 
         if ($first !== null) {
             $container->setAlias('cache', 'cache.provider.'.$first);
+            $container->setAlias('php_cache', 'cache.provider.'.$first);
         }
     }