Update NuMCMC conversion to account for Empirical Priors

[KSkwarczynski]

Since 1.1.0 NuMCMC Tools allow storing empirical priors like Daya Bay etc.
Right now, our conversion doesn't support it :(

Talked with Asher and his preference would be that this isn't done by default bur rather we have a separate app which adds empirical priors.