- makes for clearer code

ENH: make writeIfDifferent part of Ostream

GeometricField: Renamed internalField() -> primitiveField() and dimensionedInternalField() -> internalField()

These new names are more consistent and logical because:

primitiveField():
primitiveFieldRef():
    Provides low-level access to the Field<Type> (primitive field)
    without dimension or mesh-consistency checking.  This should only be
    used in the low-level functions where dimensional consistency is
    ensured by careful programming and computational efficiency is
    paramount.

internalField():
internalFieldRef():
    Provides access to the DimensionedField<Type, GeoMesh> of values on
    the internal mesh-type for which the GeometricField is defined and
    supports dimension and checking and mesh-consistency checking.

in case of tmp misuse.

Simplified tmp reuse pattern in field algebra to use tmp copy and
assignment rather than the complex delayed call to 'ptr()'.

Removed support for unused non-const 'REF' storage of non-tmp objects due to C++
limitation in constructor overloading: if both tmp(T&) and tmp(const T&)
constructors are provided resolution is ambiguous.

The turbulence libraries have been upgraded and '-DCONST_TMP' option
specified in the 'options' file to switch to the new 'tmp' behavior.

Code and tutorial case provided by Juho Peltola

Patch provided by Juho Peltola

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