Simplified the API:
- removed OrientableNormal_3, PointWithOrientableNormal_3, ReconstructionTriangulation_3, ReconstructionVertexBase_3 concepts.
- classes Orientable_normal_3, Reconstruction_triangulation_3 abd Reconstruction_vertex_base_3 are not documented anymore.
- For free functions provided with 2 variants mutable/non mutable, removed the non mutable one.
TODO:
- remove Orientable_normal_3 class.
- modify mst_orient_normals() to return an iterator over the first non oriented normal.
- fix Poisson MFC demo which does not compile anymore.