cleanup/organization of oplsaa; factored out neighbor checking function
cleanup/organization of oplsaa; factored out neighbor checking function

iModels/mbuild,Jonestj1/mbuild,iModels/mbuild,tcmoore3/mbuild,ctk3b/mbuild,sallai/mbuild,sallai/mbuild,summeraz/mbuild,tcmoore3/mbuild,ctk3b/mbuild,Jonestj1/mbuild,summeraz/mbuild