Add volume computation support and motivation

[vissarion]

This is a feature request for volume computation (implemented in volesti) to be included in dingo.

Apart from being a fundamental computation there is resent motivation from the area of metabolic networks [1] where they compute the volume of a V-polytope (a polytope given as the convex hull of its vertices). There are also computations of the intersection and union of V-polytopes.

[1] Régimbeau et al. - Contribution of genome-scale metabolic modelling to niche theory