* TaskTypeMilling returns a tuple of (moves, parameters) - instead of a
  complete Toolpath instance
* ToolpathCrop uses the Crop filter instead of the object methods for cropping
* ToolpathGrid uses the Copy filter instead of just calling "list(..)"
* ToolpathCrop and ToolpathGrid use "add_new" instead of "append" for new
  Toolpaths