add example for unclamped B-splines to show wrong implementation
add example for unclamped B-splines to show wrong implementation

The B-spline algorithms in "The NURBS Book" by Piegl & Tiller
seems to be optimized for clamped B-splines or both
ezdxf & geomdl got unclamped B-spline evaluation wrong!

mozman/ezdxf,mozman/ezdxf,mozman/ezdxf,mozman/ezdxf,mozman/ezdxf