[FrameworkBundle][DoctrineBundle] Adding a few shortcut methods
[FrameworkBundle][DoctrineBundle] Adding a few shortcut methods

This adds to convience methods, for two separate reasons:

* Controller::getDoctrine() - this will allow method completion on the Registry class to work in IDEs, is slightly shorter, and should feel very "concrete" to beginners

* Registry::getRepository() - the repository is a very convenient thing to need - this allows it to be fetched much more succintly

Overall Before:

    $product = $this->get('doctrine')
        ->getEntityManager()
        ->getRepository('AcmeDemoBundle:Product')
        ->find($id);

Overall After (with IDE method auto-completion for `getRepository`):

    $product = $this->getDoctrine()
        ->getRepository('AcmeDemoBundle:Product')
        ->find($id);

symfony/framework-bundle