Copy the color of the polygons on difference operations

[breiler]

With this change it will use the color of the intersecting shape to be used on the clipped plane of a shape:

CSG cube1 = new Cube(1)
        .toCSG()
        .move(-0.5, 0, 0)
        .setColor(Color.BLUE);

CSG cube2 = new Cube(1).toCSG().move(0.49, 0, 0)
        .setColor(Color.RED);

CSG model = cube1.difference(cube2).scale(0.4);

Which will result in this blue cube with one red face:
Screencast from 2024-08-13 19-27-15.webm

This can now be used in a bit more complex operations:
Screencast from 2024-08-13 19-32-14.webm

Adresses the issue #56

[madhephaestus]

released in 1.6.3!

[breiler]

Excellent, thanks!