Couple of inlines are needed to avoid duplication of functions between compilation units
Add tests for all binary pairs Add conversion script for HFC mixture xi and zeta
Also allow paths to be optional
Previously you always got Lorentz-Berthelot no matter what
Not yet fixed for mixtures
See https://pubs.acs.org/doi/abs/10.1021/acs.iecr.1c00847
Small computational speed bonus
