Add cam groove option to Sketch_On_Surface

[alpdigitech]

The option for Thickness in Settings is always radial/normal meaning the distance becomes between curves become smaller as you approach the origin of a cylinder curve. Add option to maintain distance between curves or paths as thickness is increased or becomes negative. This is useful to make cam grooves on a drum. Or just etch a path with constant width on a circular surface like Part WB "Create projection on surface". Maybe a hack would be to draw lots of perpendicular cylinders in a curve path.