title: Prestashop - Product admin : autocomplete is not called
body: <p>I added a custom field named product_type in Product admin. It works well, but now, I'm trying to add an autocomplete to this field. </p>
  
  <p>Here is my code (in <code>\mysite\admin\themes\default\template\controllers\products\informations.tpl</code>)</p>
  
  <pre><code>&lt;td style="padding-bottom:5px;"&gt;
      &lt;input size="55" type="text" id="product_type" name="product_type" value="{$product-&gt;product_type|escape:html:'UTF-8'}" style="width: 130px; margin-right: 5px;" /&gt;
      &lt;script type="text/javascript"&gt;
          $(document).ready(function() {
              $('#product_type').autocomplete({
                  source: function(request, response) {
                      $.ajax({
                          url: "ajax.php",
                          dataType: "json",
                          data: { term: request.term, ajaxProductType: 1 },
                          success: function(data) { response(data); }
                      });
                  },              
                  minLength: 3,
                  select: function( event, ui ) {
                      $(this).val(ui.item.value);
                  }
              });
          });
      &lt;/script&gt;
  &lt;/td&gt;
  </code></pre>
  
  <p>When I write in the field, nothing happen. The autocomplete is not called. No error in console. However, when I put an <code>alert()</code> in the <code>document.ready</code> function, it shows. So, why my autocomplete doesn't work?</p>
  
  <p><strong>Version :</strong> <em>Prestashop 1.5.6</em></p>
  
  <p>Thanks in advance for your help</p>