Add vectorized parseSBMLNotesField

This is another step towards vectorizing the convertSBMLToCobra function as we move towards supporting the SBML FBC package and move things from the notes to annotation field. These changes add the rxnGeneMat to the fields returned by parseSBMLNotesField.m, and edit the convertSBMLToCobra calls to that function to reflect the change. I have tested backwards compatibility by making sure the conversion of the iND750 model is unchanged by my code modifications.

I anticipate doing a similar change to parseSBMLAnnotationField next week, then attacking some more serious rewriting of convertSBMLToCobra after that.