Handling Cuts - 4

I think the classification function which assigns a category to each face containing an edge of the cut now works. It was surprisingly complex and I would like to turn the code into multiple small functions, but there is very few overlapping code and no clear boundaries. The thing is just a huge amount of set operations. And it isn't even complete yet, the case where three edges meet at a vertex is not even handled. But I think it is easy to integrate.

Anyhow, next is the step to integrate it in the functions which create the equations and then into the function which turns the result back into a uv-mapping. If that works, I will work on the generalized problem with multiple edges joining at on vertex.