ENH: added timeFunctionObject virtual class in inheritance hierarchy

- simply a functionObject with an additional Time reference, which is
  a combination frequently used by concrete functionObjects

src/functionObjects/utilities/setTimeStep/setTimeStepFunctionObject.C

@@ -53,28 +53,14 @@ Foam::functionObjects::setTimeStepFunctionObject::setTimeStepFunctionObject
     const dictionary& dict
 )
 :
-    functionObject(name),
-    time_(runTime)
+    timeFunctionObject(name, runTime)
 {
     read(dict);
 }
 
 
-// * * * * * * * * * * * * * * * * Destructor  * * * * * * * * * * * * * * * //
-
-Foam::functionObjects::setTimeStepFunctionObject::~setTimeStepFunctionObject()
-{}
-
-
 // * * * * * * * * * * * * * * * Member Functions  * * * * * * * * * * * * * //
 
-const Foam::Time&
-Foam::functionObjects::setTimeStepFunctionObject::time() const
-{
-    return time_;
-}
-
-
 bool Foam::functionObjects::setTimeStepFunctionObject::adjustTimeStep()
 {
     // Wanted timestep

src/functionObjects/utilities/setTimeStep/setTimeStepFunctionObject.H

@@ -69,7 +69,7 @@ SourceFiles
 #ifndef functionObjects_setTimeStepFunctionObject_H
 #define functionObjects_setTimeStepFunctionObject_H
 
-#include "functionObject.H"
+#include "timeFunctionObject.H"
 #include "Function1.H"
 
 // * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * //
@@ -80,23 +80,20 @@ namespace functionObjects
 {
 
 /*---------------------------------------------------------------------------*\
-                  Class setTimeStepFunctionObject Declaration
+         Class functionObjects::setTimeStepFunctionObject Declaration
 \*---------------------------------------------------------------------------*/
 
 class setTimeStepFunctionObject
 :
-    public functionObject
+    public functionObjects::timeFunctionObject
 {
-    // Private data
-
-        //- Reference to the time database
-        const Time& time_;
+    // Private Member Data
 
         //- Time step function/table
         autoPtr<Function1<scalar>> timeStepPtr_;
 
 
-    // Private member functions
+    // Private Member Functions
 
         //- No copy construct
         setTimeStepFunctionObject(const setTimeStepFunctionObject&) = delete;
@@ -123,14 +120,11 @@ public:
 
 
     // Destructor
-    virtual ~setTimeStepFunctionObject();
+    virtual ~setTimeStepFunctionObject() = default;
 
 
     // Member Functions
 
-        //- Return time database
-        const Time& time() const;
-
         //- Called at the end of Time::adjustDeltaT() if adjustTime is true
         virtual bool adjustTimeStep();