A function to fit a Bezier curve to a set of dot-to-dot points

[JackBuck]

Whilst not essential, this is (in my mind) most desirable of the highly desirables, and it won't be too difficult.

My idea is to:

• class each node as a cusp or a smooth node, based on the angle to the nodes either side (e.g. if the angle is <90 degrees then it is a cusp),
• for smooth nodes, use the inkscape autosmooth algorithm:
  • Let PQR be a set of three consecutive nodes
  • Compute a unit vector u perpendicular to the angle bisector for PQR, whose projection points from P to R
  • Denoting the handles of Q as Q+ and Q-, let Q+ = Q + u dist(QR)/3 Q- = Q - u dist(PQ)/3
• for cusp nodes, try retracting the handles (so that the node and both handles are at the same location)