title: tooltip for WMS points with geoext
body: <p>My idea is to get tooltip contains information about the point ,
  these points return from WMS layer, 
  i tried these ways:</p>
  
  <p>1- with vector layer there is "graphictitle" when styling the points and it display a tooltip,
  but with WMS i could not find property to use it as a tooltip in SLD(wms styling).</p>
  
  <p>2- when i use ext tooltip , its return wrong location because i don't know what the target .! </p>
  
  <pre><code>new Ext.ToolTip({
          target: 'no target',
          html: 'A very simple tooltip'       }).show();})
  </code></pre>
  
  <p>3- so i want to use geoext .</p>
  
  <p>can any one help ?</p>