Add a face truncation method to Polyhedron class #18128
Description
Currently, it is possible to do a truncation of a polytope via the method ".edge_truncation()".
See http://en.wikipedia.org/wiki/Truncation_%28geometry%29
I currently need the notion of edge-truncation, which is achieve by cutting the polytope along a "well-chosen" hyperplane whose normal vector lies in the normal cone of the edge. This edge truncation uses only one edge. Not all edges at once.
Further, one can define a face truncation similarly with the same code. I am implementing a method called ".face_truncation(face, normal_coefficient, cut_frac)" taking a face of the polytope, and two optional parameters to vary the angle of the cut.
This new method makes the old method ill-named. It should be renamed simply "truncation" or "complete_vertex_truncation".
While at it, I corrected a few writing conventions in the file.
CC: @vbraun @sagetrac-mhampton @mo271
Component: geometry
Keywords: face truncation, polytope
Author: Jean-Philippe Labbé
Branch/Commit: 55f9cf6
Reviewer: Vincent Delecroix, Frédéric Chapoton
Issue created by migration from https://trac.sagemath.org/ticket/18128