Linear regression for cubic Bézier curve approximation

[YenPeiChen07]

This issue is derived from PR #384 to track coding work for the linear regression.

Currently, a NACA 4-digit airfoil can be drawn in both linear approximation and cubic bezier approximation.

The next step is to calculate the L2-norm as a metric for determining cubic Bézier curve approximation.

Details for next step:

1. Get the x-axis value of sampled points on each cubic Bézier curve (pX)
2. Get the y-axis value (pY1) based on sampled point (pX)
3. Get the y-axis value from NACA parametric curve (pY2)
4. Calculate L2-norm between pY1 and pY2. (The square root of the sum of squares of the residual between pY1 and pY2)