title: Flex tooltip on spark datagrid header
body: <p>Is it possible to set a tooltip just on the header of a spark datagrid. I do not want any tooltips on the data - just the header. I have played with mouse over and this sort of looks like it might work. This seems a bit of a hack to me though.</p>
  
  <p>Can anyone help or give me any tips (pun intended)?</p>
  
  <p>Thanks</p>