the updated explicit source functionality

- Updates to solver, equations, createFields and createExplicitSources

- deprecated:
  - timeActivatedExplicitSource (old base type)
  - timeActivatedExplicitCellSource
  - timeActivatedExplicitMulticomponentPointSource

- introduced timeActivatedExplicitSource
  - templated on primitive type - scalar, vector, tensor...
  - takes as input, either a cell set or list of points

     reacting multi-phase level of cloud/parcel

- changes to createClouds.H
- updated tutorial cases to reflect changes

timeVaryingMappedFixedValueFvPatchField: Added the option to specify the name of the field data table.

Defaults to the name of the field the BC is being applied to but may be set
using the keyword fieldTableName, e.g.

    fieldTableName  totalPressure;

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.

    to the returnReduce() function that led to some odd behaviour.

pointsInstance.

For now also dump topology related sets to pointsInstance since otherwise
paraFoam cannot see them (only looks at first 'sets' directory when searching
back)

This comes up when displaying sets on moving meshes. The topology does not
change so the set should stay the same.

- Earlier calculation of dQ was misleading - gave a measure of temperature
  change and not heat release - also mixed molar/mass units so value was
  somewhat random
- Updated to calculate enthalpy/sec [m2/s3] and improved/more descriptive
  comments

- Left over from earlier commit 2900792f

Removed #include file

- added directMapped*Patch constructors with uniform offset
- changed splitMeshRegions to use it
- adapted chtMultiRegionFoam tutorials

- info now written as strings
- info now collected on master processor and written to top level
  postProcessing folder as postProcessing/lagrangian/<cloudName>/<time>/...

The refValue was being converted by mixedEnthalpy (even though it is not
used) so a sensible value is necessary to get it to go through the conversion.
So it now just gets the value

The boundary conditions were still accessing e.g. the temperature even
when restarting. Now they
will reread all their data if there is a 'value' field present.

An empty list (m_) has no pointer so cannot be referenced. Instead we
now return a null pointer (which is no problem for UList)