Added a mockup of how one would hardcode models into the shared library (a la CoolProp), dynamic loads just need to be replaced with hardcoded strings, probably encoded as binary

Couple of inlines are needed to avoid duplication of functions between compilation units

Add third density derivatives to sat_Z_accuracy.cpp (remarkably, even better than the first derivative)

Add tests for all binary pairs
Add conversion script for HFC mixture xi and zeta

Not yet fixed for mixtures