* Add ability to access a single departure term in a multi-fluid model

* Bump version to dev

* Split out reducing and mutants to their own headers

* Remove unused function

Refactor to avoid duplication

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

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

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