Useless vectors are commented out, will we fully remove them?

Bug fix due to misunderstanding of
  _species_reactant_stoichiometry
  _species_product_stoichiometry
  _species_delta_stoichiometry
with respect to
  _reactant_stoichiometry
  _product_stoichiometry

The three former vectors over all the species are useless and commented out.
_gamma calculation is made with the latter vectors.