Needs some testing yet, and to be made a first-class citizen

See https://en.cppreference.com/w/cpp/types/result_of

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

Expose more critical methods in pybind11 interface

Also not clear if this is the best way to include it.  Probably need the std::variant approach here too.

Python compilation working again

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