configurator: fix (a bit) invalid HTML

Insert fields in a <div>, not in a <table>, fields are not valid table
elements (they are not <tr>).

Configurator still produce invalid HTML, this seem to be the minimal fix
to have matrixboxs rendered properly without having to rewriting all
configurator page templates.

bt5/erp5_configurator/SkinTemplateItem/portal_skins/erp5_configurator_wizard/form_empty.zpt

@@ -65,11 +65,11 @@
                     <table width="100%" class="Border">
                       <tr>
                         <td tal:repeat="cell row" valign="top">
-                          <table width="100%">
+                          <div width="100%">
                             <tal:block tal:repeat="field python:form.get_fields_in_group(groups[cell])">
                               <tal:block metal:use-macro="here/field_render/macros/field_render"/>
                             </tal:block>
-                          </table>
+                          </div>
                         </td>
                       </tr>
                     </table>