Checkpointing implementation of Random class; about to redesign away from virtual functions using templates

Fix issue with templated callSync function so that it can be used easily on functions taking rvalue arguments

Added 4-particle vecangle potential; untested, and configuration.cpp still needs to build the potential dictionary using type,filename tuples as keys

Changed BondAngle to be the product of the energy of potentials applied to the central bond and two angles formed by four particles