Improve accuracy of Helper.cubicRoots() #23
Description
- Use final newton root refinement in cubic roots solve to refine accuracy
- For clip intersections (xPoints, yPoints), ensure x(t) or y(t) are outside of the clip (side issue) => extra clip padding will then be useless (1.0 for float, 0.25 for double variants) as roots do not ensure enough precision on the point coordinates for now