A second order function returning an evaluator for the given 2D Kochanek–Bartels curve
param pt1- Previous point
param pt2- First point
param pt3- Second point
param pt4- Next point
param tension- The tension of the curve, [-1..1] from round to tight.
param continuity- The continuity of the curve, [-1..1] from box corners to inverted corners.
param bias- The bias of the curve, [-1..1] from pre-shoot to post-shoot.
returns A function which gives the value on the 2D Kochanek–Bartels curve at t