Switch critical tracing to use one of the molar concentrations as the fixed parameter when polishing

Expose more critical methods in pybind11 interface

Break up pybind11 interface into separate compilation units (not as beneficial as hoped); still very slow

added CMakeSettings.json for working with VisualStudio
added missing "template" to dependent template-function calls

Co-authored-by: Tobias Loew <tobi@die-loew.de>

And JSON I/O

Also add the accessors as methods of the class in the python interface (overload resolution has large runtime overhead)

And Python wrapper and tests

Add test for neff; it is undefined for vdW EOS, interesting

Scary warning from MSVC:
4>C:\Program Files (x86)\Microsoft Visual Studio\2019\Professional\VC\Tools\MSVC\14.28.29333\include\cmath(638): warning C4717: 'copysign<double,double,0>': recursive on all control paths, function will cause runtime stack overflow