Interpolate attributes when splitting mesh

[BrunoLevy]

Operations that modify a mesh (mesh_split, mesh_intersection) do not interpolate vertex and facet corner attributes.

• [x] Add generic interpolation functions to AttributeManager
• [x] Wire the callbacks in mesh_split
• [x] Have an option in MeshSurfaceIntersection, write it as a post-processing function, right before killing the original facets that were split
• [ ] attributes-aware simplify_coplanar_facets() (this one I'm unsure I'll do it, we'll see...)