Now that the dispatcher does its own TryExecute, filters do not need to
do that. This change requires all worklets called by filters to be able
to execute without knowing the device a priori.
This commit adds a worklet as well as a filter that modify point coordinates by moving points
along point normals by the scalar amount times the scalar factor.
It's a simpified version of the vtkWarpScalar class in VTK. Additionally the filter doesn't
modify the point coordinates, but creates a new point coordinates that have been warped.