Allows the specification of a reference height, for example the height
of the free-surface in a VoF simulation, which reduces the range of p_rgh.

hRef is a uniformDimensionedScalarField specified via the constant/hRef
file, equivalent to the way in which g is specified, so that it can be
looked-up from the database.  For example see the constant/hRef file in
the DTCHull LTSInterFoam and interDyMFoam cases.

The old separate incompressible and compressible libraries have been removed.

Most of the commonly used RANS and LES models have been upgraded to the
new framework but there are a few missing which will be added over the
next few days, in particular the realizable k-epsilon model.  Some of
the less common incompressible RANS models have been introduced into the
new library instantiated for incompressible flow only.  If they prove to
be generally useful they can be templated for compressible and
multiphase application.

The Spalart-Allmaras DDES and IDDES models have been thoroughly
debugged, removing serious errors concerning the use of S rather than
Omega.

The compressible instances of the models have been augmented by a simple
backward-compatible eddyDiffusivity model for thermal transport based on
alphat and alphaEff.  This will be replaced with a separate run-time
selectable thermal transport model framework in a few weeks.

For simplicity and ease of maintenance and further development the
turbulent transport and wall modeling is based on nut/nuEff rather than
mut/muEff for compressible models so that all forms of turbulence models
can use the same wall-functions and other BCs.

All turbulence model selection made in the constant/turbulenceProperties
dictionary with RAS and LES as sub-dictionaries rather than in separate
files which added huge complexity for multiphase.

All tutorials have been updated so study the changes and update your own
cases by comparison with similar cases provided.

Sorry for the inconvenience in the break in backward-compatibility but
this update to the turbulence modeling is an essential step in the
future of OpenFOAM to allow more models to be added and maintained for a
wider range of cases and physics.  Over the next weeks and months more
turbulence models will be added of single and multiphase flow, more
additional sub-models and further development and testing of existing
models.  I hope this brings benefits to all OpenFOAM users.

Henry G. Weller

Improve code reuse
Add multiphaseInterDyMFoam
Retire MRFinterFoam -> now handled by interFoam with fvOptions
Update tutorials

Needs to be consolidated with multiphaseInterFoam with thermal and
compressibility effects made run-time selectable

fixedFluxPressure BC: the snGrad is now pushed into the BC from pEqn.H rather than being evaluated in the BC

Multiphase: Update all solvers to accommodate the split between twoPhaseMixture and incompressibleTwoPhaseMixture

This reverts commit c5bea524.

This reverts commit b18f6cc1.

Exception: applyWallFunctionBoundaryConditions.C cannot split #include
directives.

uniformDimensionedVectorField.

location for the specification is the same as that for the pd level.

- change system/controlDict to use functions {..} instead of functions (..);
  * This is internally more efficient
- fixed formatting of system/controlDict functions entry

- pedantic change: use 'return 0' instead of 'return(0)' in the applications,
  since return is a C/C++ keyword, not a function.

Changed formatting of interDyMFoam