Make handling of Reactor Wall functions consistent

[ischoegl]

Abstract

Reactor walls define wall_Q as well as wall_vdot in clib, which have an explicit time dependency although the time is known internally (see Cantera/cantera#1182 (comment)). The Python API provides non-pythonic setters, and omits getters. An improved solution should be implemented that is consistent across all interfaces.

Motivation

Describe the need for the proposed change:

• What problem is it trying to solve? ... inconsistent/incomplete interface
• Who is affected by the change? ... new Matlab Interface Matlab toolbox revamp cantera#1182
• Why is this a good solution? ... consistent interface

Possible Solutions

Update underlying C++ functions as needed and adapt Python/Matlab API's.

References

Cantera/cantera#1182