title: Increase label index in symfony2 form from the controller
body: <p>I'm looking for a way to get label index to show it with every field from sonata_type_collection: 
  Actually I used this code in the configureFormFields function of my admin class:</p>
  
  <pre><code> -&gt;add('TrainingGoals', 'sonata_type_collection', array(
                      'by_reference' =&gt; false,
                      'btn_add' =&gt; false,
                      'required' =&gt; false,
                      'label' =&gt; true,
                      'type_options' =&gt; array('delete' =&gt; false),
                      'cascade_validation' =&gt; true,
                          ), array(
                      'edit' =&gt; 'inline',
                      'inline' =&gt; 'table',
                  ))
  </code></pre>
  
  <p>And I use this function to render only five instance of the goals form:</p>
  
  <pre><code>public function getNewInstance() {
          $object = parent::getNewInstance();
  
          for ($i = 0; $i &lt; 5; $i++) {
  
              $trainingGoals = new TrainingGoals();
              $trainingGoals-&gt;setGoal('');
              $trainingGoals-&gt;setTraining();
              $object-&gt;addTrainingGoal($trainingGoals);
          }
          return $object;
      }
  </code></pre>
  
  <p>But I get only one label for all rendred fields, does this make any sense ? How can I render label like this :</p>
  
  <pre><code> Goals 1:
   Goals 2:
   Goals 3: 
   ...
  </code></pre>