Implement PSR-11

Delegate lookup is optional and thus, not implemented.

Author: greg0ire

Resources/config/services.xml

@@ -40,6 +40,7 @@
             <argument type="collection" />
         </service>
 
+        <service id="Psr\Container\ContainerInterface" alias="service_container" public="false" />
         <service id="Symfony\Component\DependencyInjection\ContainerInterface" alias="service_container" public="false" />
         <service id="Symfony\Component\DependencyInjection\Container" alias="service_container" public="false" />