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.

applications/utilities/preProcessing/setFields/setFields.C

@@ -88,7 +88,7 @@ bool setCellFieldType
 
         if (selectedCells.size() == field.size())
         {
-            field.internalFieldRef() = value;
+            field.primitiveFieldRef() = value;
         }
         else
         {