Add overview of Python/Cython/C++ interactions

[ischoegl]

Abstract

Cantera is implemented in C++, while Cython serves as the interface to the Python API, which presumably is the main interface Cantera users are using.

While the topic is advanced, it would be useful to provide an overview of how the C++ core interacts with the Python front end, as well as how C++ objects receive data from YAML input files.

A similar issue exists for the clib C-interface used by new MATLAB and C# interfaces.

Motivation

Describe the need for the proposed feature:

• What problem is it trying to solve? ... provide a quick overview to new dev's
• Who is affected by the change? ... users interested in the inner workings of Cantera
• Why is this a good solution? ... it hopefully improves the learning curves and increases community participation

Possible Solutions

Add a *.md file to the doxygen documentation.