Called when the user drags rows with cellSelectionMode=false
Drag occurs when allowDrag=true and the user drags or clicks and-holds with allowdragreorder=true
Modify drag to customize image/data
drag.PrivateRawData("rows") is XML representing the rows being dragged.
Return true to allow the drag.


Example:

//allows rows to be dragged or click-hold to drag

Return true //allow the drag