Make CVUniverse take parameters from json config

[hschellman]

Some calculations in CVUniverse use parameters that are currently hardwired.
Suggest coding a way to set them analogous to the way we set.

Main program
PlotUtils::MinervaUniverse::SetAnalysisNuPDG(config["pdg"])

In MinervaUniverse:
PlotUtils/MinervaUniverse.h: static int GetAnalysisNuPDG();
PlotUtils/MinervaUniverse.h: static bool SetAnalysisNuPDG(int nu_pdg);

Look at the logic for setting and getting pdg (or other variables) and use those to set a paraemter you want.