speed up addEquivalents (a lot).  also add methods to return full e-bond representation of diagrams.
speed up addEquivalents (a lot).  also add methods to return full e-bond representation of diagrams.

etomica/etomica,etomica/etomica,ajschult/etomica,ajschult/etomica,ajschult/etomica,etomica/etomica