Dissociation and Genetic Production Interaction Nodes in SBML export

[travisformayor]

There are 4 types of Interaction Nodes: Non-Covalent Binding, Biochemical Reaction, Dissociation, and Genetic Production. Non-Covalent Binding export is already supported, and adding Biochemical Reaction export is tracked in #429 and #431.

This issue covers the rest of the types that still need SBML export: Dissociation and Genetic Production.