Update the Controller to be consistent

We are always using $this->container->get() and now we're using the short-cut sometimes to access to a service.
It could be nice to stay with $this->container->get() to stay consistent and for those who copy and paste the Controller to create a ControllerUtils, they wont have to change it (in fact neither ControllerUtils::get() nor ControllerUtils::has() exists).
See: http://www.whitewashing.de/2013/06/27/extending_symfony2__controller_utilities.html