This change means that getApplication still works if we have a
controlDict.orig, rather than a controlDict. This allows us to simplify
the scripting of tutorials in which the controlDict is modified.
Introduced thermalPhaseChangePopulationBalanceTwo- and MultiphaseSystem as
user-selectable phaseSystems which are the first to actually use multiple mass
transfer mechanisms enabled by
commit d3a237f560.
The functionality is demonstrated using the reactingTwoPhaseEulerFoam
wallBoilingPolydisperse tutorial.
Patch contributed by VTT Technical Research Centre of Finland Ltd and Institute
of Fluid Dynamics, Helmholtz-Zentrum Dresden - Rossendorf (HZDR).
