title: Symfony Form Collection won't remove element
body: <p>Form Type</p>
  
  <pre><code>public function buildForm(FormBuilderInterface $builder, array $options)
  {
      $builder
              ......
              -&gt;add('menores', 'collection', array(
                  'type' =&gt; new CotizacionMenorType(),
                  'allow_add' =&gt; true,
                  'allow_delete' =&gt; true,
                  'by_reference' =&gt; false,
                  'required'  =&gt; false
              ))
              ......
      ;
  }
  </code></pre>
  
  <p>Controller</p>
  
  <pre><code>public function editarAction(Cotizacion $cotizacion, Request $request)
  {
  
      $pageData['accion'] = 'Editar';
  
      $objForm = $this-&gt;createForm(new EditarCotizacionType(), $cotizacion);
  
      $objForm-&gt;handleRequest($request);
  
      if ($objForm-&gt;isValid()) {
          echo '&lt;pre&gt;';
          echo \Doctrine\Common\Util\Debug::dump($cotizacion-&gt;getMenores());
          die('&lt;/pre&gt;');
          .............
      }
      .......
  }
  </code></pre>
  
  <p>When I render the form and remove form the DOM 1 element, then I submit the form and the elements still in the coleccion., when I print de <code>$cotizacion-&gt;getMenores()</code> the removed element still there</p>
  
  <p>Thanks</p>