code: public int addWidget (Widget widget, int colSpan, String... styles)
      {
          int row = getRowCount();
          setWidget(row, 0, widget, colSpan, styles);
          return row;
      }
docs: Adds a widget to the bottom row of this table in column zero, with the specified column span
  and style.
  
  @return the row to which the widget was added.