title: Symfony2 - Set translation domain for a whole form
body: <p>I want to translate a form created with symfony's formbuilder. As i don't want one big translation file it is <a href="http://symfony.com/doc/current/book/translation.html#using-message-domains">splitted up</a> into "domains".</p>
  
  <p>Now i have to specify the <code>translation_domain</code> for each form-field, otherwise symfony will look in the wrong file. This option has to be added to every field and i'm wondering if there is a way to set this option to a whole form?</p>
  
  <p><strong>Sample code i'm not happy with:</strong></p>
  
  <pre><code>$builder-&gt;add(
      'author_name',
      'text',
      array('label' =&gt; 'Comment.author_name', 'translation_domain' =&gt; 'comment')
  )-&gt;add(
      'email',
      'email',
      array('label' =&gt; 'Comment.email', 'translation_domain' =&gt; 'comment')
  )-&gt;add(
      'content',
      'textarea',
      array('label' =&gt; 'Comment.content', 'translation_domain' =&gt; 'comment')
  );
  </code></pre>