functionObjects: Simplified the handling of the post-processing mode

Replaced the 'postProcess' argument to the 'write' and 'execute'
functions with the single static member 'postProcess' in the
functionObject base-class.

src/functionObjects/field/fieldCoordinateSystemTransform/fieldCoordinateSystemTransform.H

@@ -145,10 +145,10 @@ public:
         virtual bool read(const dictionary&);
 
         //- Calculate the transformed fields
-        virtual bool execute(const bool postProcess = false);
+        virtual bool execute();
 
         //- Write the transformed fields
-        virtual bool write(const bool postProcess = false);
+        virtual bool write();
 };