Add a second Ek cut for specific particles

[Laurie Nevay]

I’ve added the ability to exclude some particles (by PDG ID) from the general option, minimumKineticEnergy=X*GeV cut. These are tracked down to 0 energy / the range cuts. However, it would be useful to have a 2nd cut for select particles.

For example, general cut 10 GeV in high energy model. Muons cut at 1*MeV, neutrinos excluded from cuts.

The userlimits class should be kept as simple as possible as it will be checked every step of every track in every volume. So it’s suitable to specialise this class and only attach the right type when required perhaps.