functions.

only so far.  Wall force model hard-coded.

so move everything to a vectorField or a pointField.  Changed accessor
for a ReferredCells points to points().

Renamed PairFunction to PairModel, so will fit in with WallModel,
rather than WallFunction, a confusion waiting to happen.

of the referred cells.  To be used by wall interactions.

the InteractingKinematicParcel, using in the SpringSliderDashpot
model.  Correctly determining extreme properties for the timestep
subCycling calculation.

than when it is initialised.  This allows messages to be created and added to.

wall patch faces that each cell is potentially in range of.

which faces are from wall patches.

Moving ReferredCell into a subdirectory of ReferredCellList.

determines the number of subcycles needed to satisfy its timestep
requirements.