Remove equals overriding of BioEntity and protects creation of BioParticipant
- Two bioentity were equals if they had the same id. Now, the two objects must be equal.
- Constructors of BioEnzymeParticipant and BioReactant are now "protected". This avoids to create redundant participants. A BioCollection for each one has been created in the BioNetwork
- The constant parameter is not saved anymore when loading a SBML file. It's not used in Met4j applications. If we want to save reactant attributes, we have to do at the reaction level now.