path_extrude with scaling

I enjoyed gringer's path_extrude, but I really wanted a way to scale along the path. I saw halfshavedyaks' remix on this, although I was seeing issues where when making a full loop, the profile flips so as to be oriented with the original profile again when going back the other direction. I found it easier to snatch HSY's simple scalepoints2D function and toss it into gringer's original code to add scaling than to try to fix the flipping issue.

2019-01-27: added V2, which includes scaling in both X and Y.
2019-05-16: added V3, which has new safeCap argument for capping your (potentially non-planar, float imprecision) profile with triangles, making it compile safely on older versions.