BUG: The vtkPicker and vtkAreaPicker were inconsistent in what they added to the Prop3Ds pick list (i.e. all hit props) vs. what they generated PickEvents for (only the hit props that were closer that any prop that had previously been hit during the pick).  Now, for all pickers, only one PickEvent is generated, and it is only generated for the hit prop that is closest to the camera.  In vtkRenderedAreaPicker, the PickEvent was moved to the end of the pick to make sure that Mapper, DataSet, etc. are set before it is generated.