While p and pmh (pd in OpenFOAM-1.5.?) are equivalent on orthogonal meshes they
are not on non-orthogonal meshes and the difference is very important for
buoyancy-dominated flows such as settling.  settlingFoam is now written in terms
of pmh (static pressure minus hydrostatic pressure) which used to be called pd
but that confused too may people.

buoyantPressureFvPatchScalarField: added support for pmh (pressure - hydrostatic) which is the new name for pd.

Added numbering on searhableSurfaceCollection.

- moved to $FOAM_LIBBIN/paraview so that built libraries sit in their
  own folder - avoids PV error msgs on start-up when it tries to load
  all libs under the $PV_PLUGIN_PATH

- using chemical enthalpy instead of total enthalpy

- Re-setting initial T fields to unitialised values prior to running
  setFields utility

- Retrieve h directly from thermo package instead of using look-up

- removed repeated declaration of pure abstract functions
- added function to return the turbulence effective thermal diffusivity
  for a patch

- Corrected calculation of temperature gradient
- Option to specify the heat source in terms of a power [W] or flux [W/m2]

- Updates to enable correct operation in parallel
- Added weighted average operation for cell sources