title: Multiple filter in sonata admin
body: <p>I want to have that a filtered field in sonata admin datagrid mapper can be OR or AND connected with the user given filter values ... for example the field "Name" can be "John" or "Sandy" ...
  In the docs on <a href="https://sonata-project.org/bundles/doctrine-orm-admin/master/doc/reference/filter_field_definition.html" rel="nofollow noreferrer">https://sonata-project.org/bundles/doctrine-orm-admin/master/doc/reference/filter_field_definition.html</a> they write</p>
  
  <pre><code> -&gt;add('tags', null, array(), null, array('expanded' =&gt; true, 'multiple' =&gt; true))
  </code></pre>
  
  <p>where i aspect, that the keword "multiple" should allow a field to be added multiple times ... but all i get is, that "multiple" and "expanded" is not a valid option for this field.</p>
  
  <p>How can i let the user filter by AND or OR conditions?</p>
  
  <p>Thanks</p>