title: Reload or clear data in existing form in Symfony2.1
body: <p>We upgraded from Symfony 2.0 to 2.1. With 2.0, I used to modify the entity and reload the form like this:</p>
  
  <pre><code>$form-&gt;setData($entity);
  </code></pre>
  
  <p>But this is not allowed anymore with Symfony 2.1 (<a href="https://github.com/symfony/symfony/pull/3322">https://github.com/symfony/symfony/pull/3322</a>). I get the following error:</p>
  
  <pre><code>You cannot change the data of a bound form
  </code></pre>
  
  <p>Is there a way to rebind the form to the entity/reload the data?</p>