title: Raw filter on Sonata Admin Bundle configureShowFields
body: <p>I'm doing a project with Symfony2 and Sonata Admin Bundle.
  How I can apply the filter raw of twig (to display formated text) in action configureShowFields?</p>
  
  <p>I would not override Sonata templates...</p>
  
  <p>The code of my configureShowFields:</p>
  
  <pre><code>protected function configureShowFields(ShowMapper $showMapper)
      {
          $showMapper
              -&gt;add('active')
              -&gt;add('title')
              -&gt;add('subtitle') // I need this field with twig RAW filter
              -&gt;add('description') //I need this field with twig RAW filter
              -&gt;add('url')
              -&gt;add('date')
              -&gt;add('tags')
              -&gt;add('file');
      }
  </code></pre>