title: there is no default value + symfony2 + crud
body: <p>sf 2.8.4 with sylius 0.17</p>
  
  <p>i had generated a controller and routes with generate:doctrine:crud</p>
  
  <p>i can list all datas, but on show and edit, always got this error:</p>
  
  <pre><code>Controller "St\AppBundle\Controller\TranslationDomainController::showAction()" requires that you provide a value for the "$translationdomain" argument (because there is no default value or because there is a non optional argument after this one).
  </code></pre>
  
  <p>here the show action</p>
  
  <pre><code>    public function showAction(TranslationDomain $translationdomain)
  {
      $deleteForm = $this-&gt;createDeleteForm($translationdomain-&gt;getId(), 'administration_translations_domain_delete');
  
      return $this-&gt;render('StAppBundle:TranslationDomain:show.html.twig', array(
          'translationdomain' =&gt; $translationdomain,
          'delete_form' =&gt; $deleteForm-&gt;createView(),        ));
  }
  </code></pre>
  
  <p>and the route</p>
  
  <pre><code>administration_translations_domain_show:
  pattern:  /{id}/show
  defaults: { _controller: "StAppBundle:TranslationDomain:show", id : 1 }
  requirements:
      id : \d+
      _method : get
  </code></pre>