Update NSI oscillation source files, add stan support

[xiaoyan1997]

No description provided.

[chenel]

Thanks for working with me on this.

I noticed one other thing, which is not your fault because it's from the preceding calculator code, but which needs to be addressed ASAP:

_OscCalcPMNS_NSI doesn't override GetParamsHash() from the base class. That means it inherits GetParamsHashDefault from _IOscCalcAdjustable, which only hashes the 8 standard oscillation parameters: fL, fRho, fDmsq21, fDmsq32, fTh12, fTh13, fTh23, fdCP (see IOscCalc.cxx:87-90). The 9 NSI-specific members (fEps_ee, ...) are silently excluded.
This means that any cache pull using GetParamsHash() will return stale results when only NSI parameters change---i.e., you'll get the same prediction for differing NSI parameters (😱).

We need an overridden GetParamsHash() in this class. Are you game for implementing it?