title: setting default value in symfony2 sonata admin bundle
body: <p>how can i set default value in sonata admin bundle
  the data option is missing in configureFormFields method </p>
  
  <pre><code>protected function configureFormFields(FormMapper $formMapper)
  {
      $formMapper
          -&gt;add('name', null, array('required' =&gt; true, 'data' =&gt; "my default value"))
      ;
  }
  </code></pre>
  
  <p>how can use data attribute to set default value inside field ???</p>