objectRegistry: Corrected caching of registered temporary objects

For example the generation term in the k-epsilon turbulence kEpsilon:G is a
temporary field that is specifically named and registered so that it can be
looked-up be the wall-function boundary conditions and requires slightly
different handling compared to normal temporary fields which are not registered.

The tutorials/incompressible/simpleFoam/pitzDaily case now demostrates this
functionality with the addition of

cacheTemporaryObjects
(
    kEpsilon:G
);

functions
{
    #includeFunc writeObjects(objects = (kEpsilon:G))
}

in controlDict which caches kEpsilon:G and writes it at every write time.

tutorials/incompressible/simpleFoam/pitzDaily/system/controlDict

@@ -50,4 +50,14 @@ functions
     #includeFunc streamlines
 }
 
+cacheTemporaryObjects
+(
+    kEpsilon:G
+);
+
+functions
+{
+    #includeFunc writeObjects(objects = (kEpsilon:G))
+}
+
 // ************************************************************************* //