Pass flint types back and forth

[alexej-jordan]

We want to be able to have different field types for computations in Oscar, e.g. have a meaningful implementation of a Polyhedron{T}. Field types coming from other parts of Oscar are usually based on Flint types, which polymake can handle.

For this cause we need to wrap the corresponding polymake type and allow it as an element type for our wrapped small objects like matrices.