Modifying the thermogenerator to use new aromatic chem graph
instead of making another copy.

Not sure if I cover all the cases we had found when we first
implemented the thermo_graph

1) If species is aromatic and found in thermo library use the value given in
thermo library. We need to ensure that different kekule forms are same
species.

2) If species is aromatic and not found in thermo library then convert to B
bonds and use that structure to generate the thermo.

3) If species is not aromatic and found in thermo library then use the
thermo library value.

4) If species is not aromatic and not in thermo library use TDGenerator to
get thermo.