CutoffOuter

class VisitModelCutoffOuter : public feasst::VisitModel: Similar to VisitModel, except that the distance between the first sites on two different particles are compared against the cutoff + 2*cutoff_outer (given in the fstprt files), and if that distance is beyond this outer cutoff, then all other interactions between these particles. Thus, cutoff_outer should be set to the maximum possible distance between the first site of the particle and any other site in the same particle.