title: How to translate labels in symfony2 forms with messages.en.yml?
body: <p>I am trying to get translation of form fields to work. I have <code>messages.en.yml</code> in my Bundle's Ressource folder.</p>
  
  <pre><code>test: it works
  form:
      description: Add a description.
  </code></pre>
  
  <p>I want to build a form in an <code>EntityType</code> which translates the labels of the form fields accordingly.  </p>
  
  <pre><code>$builder-&gt;add(
      'description',
      null,
      array('label' =&gt; 'form.description', 'required' =&gt; false)
  );
  </code></pre>
  
  <p>Yet only the literal string <code>'form.description'</code> gets shown, not the expected translation of <code>Add a description.</code></p>
  
  <p>The translation service and the <code>messages.en.yml</code> are loaded correctly as I can call </p>
  
  <p><code>var_dump($this-&gt;get('translator')-&gt;trans('test'));</code></p>
  
  <p>in a controller and get the translated result.</p>
  
  <p>What am I missing when I want to treat the string <code>'form.description'</code> as something that should be translated?</p>
  
  <p>I suppose I have to call the trans function on them anyhow, yet how can I make it in one go automatically? </p>