Solitude - singular algebraic surface

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

Has two holes, and two singular lines, one of which exists nakedly in the voids in the surface!

Provided are three files:
* `solitude_thickened.stl` -- has the normal vectors fixed, and is thickened for printing.
* `solitude_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 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. This version is not directly suitable for 3d printing.
* `input` -- the Bertini_real input file used to compute it.

Computed with a Numerical Algebraic Geometry program I wrote, called [Bertini_real](https://b