Fix structural rates #11
Description
Use Case
Rates for structural reactions in ReaDDy should be based on the actual number of reactant particles present, rather than the number of reactant topologies.
Acceptance Criteria
The rate function for any structural reaction depends on the current number of possible reactant particles in the topology.
Details
Structural reactions are triggered per topology rather than per particle in ReaDDy. A given topology may have multiple possible reactants in a given reaction, so the rate should be scaled by the current number of valid reactants in the reacting topology.