title: Symfony2 form - date field validation doesn't work
body: <p>When I submit form the text field containing date isn't validated although I defined constraint in entity. What is incorrect? Do I need to write custom date validator for text field containing date?</p>
  
  <p>In my form class I have</p>
  
  <pre><code>public function buildForm(FormBuilder $builder, array $options)
  {
      $builder
              -&gt;add('added', 'date', array(
                  'required' =&gt; false,
                  'widget' =&gt; 'single_text',
                  'format' =&gt; 'yyyy-MM-dd',
                  'attr' =&gt; array(
                      'class' =&gt; 'datepicker'
                  )
              ))
  }
  </code></pre>
  
  <p>In entity</p>
  
  <pre><code>/**
   * @var date
   *
   * @Assert\Date(message = "test")
   * @ORM\Column(name="added", type="date", nullable=true)
   */
  private $added;
  </code></pre>
  
  <p>And in controller (I need those errors listed)</p>
  
  <pre><code>    $request = $this-&gt;getRequest();
      $r = $this-&gt;getProfileRepository();
      $profile = $id ? $r-&gt;find($id) : new \Alden\XyzBundle\Entity\Profile();
      /* @var $profile \Alden\XyzBundle\Entity\Profile */
      $form = $this-&gt;createForm(new ProfileType(), $profile);
      if ($request-&gt;getMethod() == 'POST')
      {
          $form-&gt;bindRequest($request);
          $errors = $this-&gt;get('validator')-&gt;validate($profile);
          foreach ($errors as $e)
          {
              /* @var $e \Symfony\Component\Validator\ConstraintViolation */
              $errors2[$e-&gt;getPropertyPath()] = $e-&gt;getMessage();
          }
          if (count($errors2))
          {
          ...
          } else {
              $em = $this-&gt;getEntityManager();
              $em-&gt;persist($profile);
              $em-&gt;flush();
          }
  </code></pre>