- previously introduced `getOrDefault` as a dictionary _get_ method,
  now complete the transition and use it everywhere instead of
  `lookupOrDefault`. This avoids mixed usage of the two methods that
  are identical in behaviour, makes for shorter names, and promotes
  the distinction between "lookup" access (ie, return a token stream,
  locate and return an entry) and "get" access (ie, the above with
  conversion to concrete types such as scalar, label etc).

- 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)

- use the dictionary 'get' methods instead of readScalar for
  additional checking

     Unchecked:  readScalar(dict.lookup("key"));
     Checked:    dict.get<scalar>("key");

- In templated classes that also inherit from a dictionary, an additional
  'template' keyword will be required. Eg,

     this->coeffsDict().template get<scalar>("key");

  For this common use case, the predefined getXXX shortcuts may be
  useful. Eg,

     this->coeffsDict().getScalar("key");

- makes for clearer code

ENH: make writeIfDifferent part of Ostream

- use scalar(0) instead of scalar(0.0) etc

Avoids the clutter and maintenance effort associated with providing the
function signature string.

set the BC to fixedValue using refValues as values

This reverts commit c5bea524.

This reverts commit b18f6cc1.

eg,
    - makePatchTypeField -> makeTemplatePatchTypeField
    - makeNonTemplatedPatchTypeField -> makePatchTypeField

Exception: applyWallFunctionBoundaryConditions.C cannot split #include
directives.

- space between keyword and bracket in 'for(..)', 'if(..)', 'while(..)'

the include file back to mathematicalConstants.H to make upgrading code slightly easier.