Made modifications to rho and A operators to allow for incorporating the...

Made modifications to rho and A operators to allow for incorporating the various disjoint objects. Still finishing up the A operator and need to think about how to properly evaluate incident waves on the various disjoint surfaces using existing codebase for both the A_rhs and rho_rhs. Also modified inputs to A_rhs and rho_rhs so that gradient/divergence operations on incident potential fields are specified independently from the potential field itself.