reactingTwoPhaseEulerFoam: Enhanced support for wall boiling

Contributed by Juho Peltola, VTT

Notable changes:

    1. The same wall function is now used for both phases, but user must
       specify phaseType ‘liquid’ or ‘vapor’

    2. Runtime selectable submodels for:
       - wall heat flux partitioning between the phases
       - nucleation site density
       - bubble departure frequency
       - bubble departure diameter

    3. An additional iteration loop for the wall boiling model in case
       the initial guess for the wall temperature proves to be poor.

The wallBoiling tutorial has been updated to demonstrate this new functionality.