New lift model supporting near-wall damping using the new
wallDampingModels.

e.g.

lift
(
    (air in water)
    {
        type            wallDamped;
        lift
        {
            type            constantCoefficient;
            Cl              0.5;
        }
        wallDamping
        {
            type            linear;
            Cd              0.5;
        }
    }
);

in which a linear near-wall damping function min(y/(Cd*d), 1) is applied to the constant
coefficient lift model.  Additional wall-damping functions will be added.

and two-phase functionality separated from multiphase functionality

Includes many contributions from Juho Peltola

Multi-species, mass-transfer and reaction support and multi-phase
structure provided by William Bainbridge.

Integration of the latest p-U and face-p_U algorithms with William's
multi-phase structure is not quite complete due to design
incompatibilities which needs further development.  However the
integration of the functionality is complete.

The results of the tutorials are not exactly the same for the
twoPhaseEulerFoam and reactingTwoPhaseEulerFoam solvers but are very
similar.  Further analysis in needed to ensure these differences are
physical or to resolve them; in the meantime the twoPhaseEulerFoam
solver will be maintained.

twoPhaseEulerFoam/interfacialModels/heatTransferModels/sphericalHeatTransfer: new heat-transfer model

Model which applies an analytical solution for heat transfer from the
surface of a sphere to the fluid within the sphere.

Provided by William Bainbridge