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/components/components.H

@@ -107,7 +107,7 @@ public:
     // Member Functions
 
         //- Write the component fields
-        virtual bool write(const bool postProcess = false);
+        virtual bool write();
 
         //- Clear the component fields from the objectRegistry
         virtual bool clear();