Calyx - singular algebraic surface

Calyx, a singular algebraic surface of degree five. This is the set of real points for which
```
x^2+y^2*z^3 - z^4 = 0.
```

Has a point singularity on a cusp-line singularity.

I have provided these files:
* `Calyx_blocky_xy.stl` -- has the normal vectors fixed, and is thickened for printing.
* `calyx_medium_smooth_xy.stl` -- the blocky version, ran through the `sampler` module for `bertini_real`.
* `calyx_raw_blocky.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 instead a tangent space which is not immediately useful for 3d printing. Hence, the surface was thickened in Blender, before being passed through Microsoft's 3D Builder to fix internal geometry. The raw versions are not directly suitable for 3d printing.
* `calyx_raw_medium_smooth.stl` -- infinitely thin, but ran through `sampler` with medium tolera