title: Format for time display?
body: <p>I am making application with symfony2 and sonata-admin bundle.</p>
  
  <pre><code>public function configureListFields(ListMapper $listMapper)
  {
      $listMapper
          -&gt;addIdentifier('id')
          -&gt;add('fromDate');
  </code></pre>
  
  <p>it shows time like this </p>
  
  <pre><code>September 1, 2013 02:00
  </code></pre>
  
  <p>so I changed</p>
  
  <pre><code> -  -&gt;add('fromDate');
   +  -&gt;add('fromDate',null,array('format' =&gt; 'yyyy-MM-dd HH:mm:ss'))
  </code></pre>
  
  <p>but it still show the same.</p>
  
  <p>please give me how to use format for time display?</p>