title: Vaadin Add new column to existing table
body: <p>I'm having some problems to add new column to my table that is generated from one JPAContainer.
  The question is... I can add a new column to my existing table if my fields are inserted from JPAContainer?
  My code looks like...</p>
  
  <pre><code>persons = JPAContainerFactory.make(Users.class, PERSISTENCE_UNIT);
  persons.sort(new String[]{"niu"}, new boolean[]{true});
  table_1.setWidth("100%");
  table_1.setSelectable(true); // Hacemos que se puedan seleccionar las filas del Grid.
  table_1.setMultiSelect(false);// Selección de múltiples filas del Grid.
  
  table_1.setContainerDataSource(persons);
  table_1.addContainerProperty("admin_vis", String.class, null);
  for (Iterator i = table_1.getItemIds().iterator(); i.hasNext();) {
          Object itemIdentifier = i.next();
  
          Item item = table_1.getItem(itemIdentifier);
          String admin = (String) item.getItemProperty("admin").getValue();
          Item item1 = ((Container) table_1.getContainerProperty(String.class,   "admin_vis")).addItem("row"+i);
          if(admin.equals("Y")) {
              Property property = item1.getItemProperty("admin_vis");
              property.setValue("true");
          } else {
              Property property = item1.getItemProperty("admin_vis");
              property.setValue("false");
          }            
      }
  table_1.setVisibleColumns(new Object[] { "niu", "nom", "mail", "admin_vis" });
  table_1.setColumnHeaders(new String[] { "Niu", "Nom", "Mail", "Admin", })
  table_1.setPageLength(15);
  table_1.setImmediate(true);
  </code></pre>
  
  <p>The error that I'm having is:
  Caused by: java.lang.UnsupportedOperationException
      at com.vaadin.addon.jpacontainer.JPAContainer.addContainerProperty(JPAContainer.java:666)
      at com.vaadin.ui.AbstractSelect.addContainerProperty(AbstractSelect.java:772)
      at com.vaadin.ui.Table.addContainerProperty(Table.java:4099)</p>
  
  <p>Hope someone can help me.
  Thanks for advice!</p>