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.

src/randomProcesses/Kmesh/Kmesh.C

@@ -52,7 +52,7 @@ Foam::Kmesh::Kmesh(const fvMesh& mesh)
     boundBox box = mesh.bounds();
     l_ = box.span();
 
-    vector cornerCellCentre = ::Foam::max(mesh.C().internalField());
+    vector cornerCellCentre = ::Foam::max(mesh.C().primitiveField());
     vector cellL = 2*(box.max() - cornerCellCentre);
 
     vector rdeltaByL;