title: activeadmin, remove empty message
body: <p>In ActiveAdmin, when there are no items for the model (in my example User), it shows a default 'There are no Users yet. Create one'. </p>
  
  <p><img src="https://i.stack.imgur.com/oE65a.png" alt="There are no * yet"></p>
  
  <ol>
  <li>How can I remove this message?</li>
  <li>Is there the possibility of customizinig it on per-page basis, that is having a particular message for a particular ActiveAdmin page?</li>
  </ol>