STYLE: generalize rule for obtaining compiler stem

- The chemistryReader is only used during construction of reactingMixture
  and thus does not require public visibility.

- this scripts are largely pre-git era and not used much anymore.
  Relocate to a legacy/ sub-directory while we see if there are
  actually any still being used.

- the utility had automatic triangulation removed some time ago, but
  never changed its name.

- catch old uses with a surfaceMeshTriangulate deprecated script

- can be used as a more natural test on the iterator.
  For example, with

     HashTable<..> table;
     auto iter = table.find(...);

  Following are now all equivalent:

    1.  if (iter != table.end()) ...
    2.  if (iter.found()) ...
    3.  if (iter) ...

- similar to autoPtr and unique_ptr. Returns the pointer value without
  any checks. This provides a simple way for use to use either
  an autoPtr or a tmp for local memory management without accidentally
  stealing the pointer.

  Eg,

     volVectorField* ptr;
     tmp<volVectorField> tempField;

     if (someField.valid())
     {
         ptr = someField.get();
     }
     else
     {
         tempField.reset(new volVectorField(....));
         ptr = tmpField.get();
     }

     const volVectorField& withField = *ptr;

STYLE: make more tmp methods noexcept

- in some cases this means you could avoid an isA<> followed by
  second dynamicCast<>

- makes the intent clearer and avoids the need for additional
  constructor casting. Eg,

      labelList(10, Zero)    vs.  labelList(10, 0)
      scalarField(10, Zero)  vs.  scalarField(10, scalar(0))
      vectorField(10, Zero)  vs.  vectorField(10, vector::zero)

- they had an isType<> instead of isA<>() check

    Averages columns of cells for layered meshes.

    For each patch face, calculates the average value of all cells attached in
    the patch face normal direction, and then pushes the average value back
    to all cells in the column.

    Useful for channel-like cases where we want to average fields in the
    spanwise direction.

    Example of function object specification:
    columnAverage1
    {
        type        columnAverage;
        libs        ("libfieldFunctionObjects.so");
        ...
        patches     (front side);
        fields      (U p);
    }

    Where the entries comprise:
    \table
        Property     | Description               | Required    | Default value
        type         | type name: fieldMinMax    | yes         |
        patches      | list of patches to collapse onto | yes  |
        fields       | list of fields to process | yes         |
    \endtable