title: Sonata date range filter
body: <p>I have a sonata date range filter </p>
  
  <pre><code>protected function configureDatagridFilters(DatagridMapper $filter)
      {
          $now = new \DateTime();
          $filter
              -&gt;add('created_at', 'doctrine_orm_date_range',  array(
                      'label' =&gt; 'created_at_long',
                      'input_type' =&gt; 'text',
                      'field_options' =&gt; array(
                          'widget' =&gt; 'single_text'
  
                      )
                  )
              );
      }
  </code></pre>
  
  <p>If I enter the same date, elements with this date are not returned in my list. 
  Is there a way to tell sonata do not use strict comparaison and use "less than or equal" and "greater than or equal" operators ?</p>