Leopold - smooth algebraic surface

Leopold, a smooth algebraic surface of degree six. This is the set of real points for which
```
1000*x^2*y^2*z^2+3*x^2+3*y^2+z^2-1 = 0.
```

No singularities! Smooth everywhere!

I have provided these files:
* `leopold_fixed.stl` -- has the normal vectors fixed.
* `leopold_raw.stl` -- raw triangulation coming from Bertini_real. Since the program works in arbitrary dimensions, I make no effort to control normals from it -- they don't exist for 4- and higher-dimensional surfaces, but