Renaming vertices_and_rays

[YueRen]

Currently, vertices_and_rays does not return vertices and rays, but minimal_faces and rays_modulo_lineality. For the sake of consistency, would it be possible to:

1. Create an alias vertices_modulo_lineality for minimal_faces.
2. Rename vertices_and_rays to vertices_and_rays_modulo_lineality.

Alternatively, we could make vertices_and_rays internal and tell users to use minimal_faces and rays_modulo_lineality (as well as their maximal cell incidences) seperately.