Fixed handling of explicit reaction orders for some reactions
Fixed handling of explicit reaction orders for some reactions

For reactions with unity reactant stoichiometric coefficients, explicit values
for the forward reaction order were being ignored while setting up the
StoichManager.

Cherry-picked from trunk (r1802).


Heathckliff/cantera,imitrichev/cantera,imitrichev/cantera,Heathckliff/cantera,Heathckliff/cantera,imitrichev/cantera,imitrichev/cantera,imitrichev/cantera,imitrichev/cantera,Heathckliff/cantera,Heathckliff/cantera,Heathckliff/cantera