ENH: adding hook adjustTimeStep to function objects. The hook is called in

Time::adjustDeltaT(). It allows function objects to manipulate the time step to
    dump at adjustable times. The following options are available for output in
    function objects: timeStep, outputTime, adjustableTime, runTime, clockTime
    and cpuTime.

src/postProcessing/functionObjects/IO/writeRegisteredObject/writeRegisteredObject.H

@@ -28,8 +28,15 @@ Group
     grpIOFunctionObjects
 
 Description
-    This function object takes-over the writing of objects registered to the
-    database.
+    This function object allows specification of different writing frequency
+    of objects registered to the database. It has similar functionality
+    as the main time database through the outputControl setting:
+        timeStep
+        outputTime
+        adjustableTime
+        runTime
+        clockTime
+        cpuTime
 
     Example of function object specification:
     \verbatim
@@ -37,6 +44,7 @@ Description
     {
         type        writeRegisteredObject;
         functionObjectLibs ("libIOFunctionObjects.so");
+        exclusiveWriting     true;
         ...
         objectNames (obj1 obj2);
     }
@@ -47,8 +55,12 @@ Description
         Property     | Description             | Required    | Default value
         type         | type name: writeRegisteredObject | yes |
         objectNames  | objects to write        | yes         |
+        exclusiveWriting    | Takes over object writing | no | yes
     \endtable
 
+    exclusiveWriting disables automatic writing (i.e through database) of the
+    objects to avoid duplicate writing.
+
 SeeAlso
     Foam::functionObject
     Foam::OutputFilterFunctionObject
@@ -89,6 +101,9 @@ protected:
         //- Name of this set of writeRegisteredObject
         word name_;
 
+        //- Takes over the writing from Db
+        bool exclusiveWriting_;
+
         const objectRegistry& obr_;
 
         // Read from dictionary