normalize package:linear

Normalize a Metric functor to have unit norm. This function does not change the functor if its norm is 0 or 1.
Convert 4-dimensional projective coordinates to a 3-dimensional point. This operation may be denoted, euclidean [x:y:z:w] = (x/w, y/w, z/w) where the projective, homogenous, coordinate [x:y:z:w] is one of many associated with a single point (x/w, y/w, z/w).