Updated VeloSim and VeloRadDamage to use new 2nd metal model (optionally) if requested by SIMCOND

This code by itself should not change the Velo output. It allows new parameters which scale the 2nd metal effect with a new (better) model and makes the cluster size closer to the data in the MC. For details see the presentations in the T&A/Simulation meeting: https://indico.cern.ch/event/693499/