functionObjects: Separated writeFile and logFiles (previously writeFiles) from regionFunctionObject

Now the functionality to write single graph files or log files (vs time)
may be used in the creation of any form of functionObject, not just
those relating to a mesh region.

src/functionObjects/field/histogram/histogram.C

@@ -50,7 +50,7 @@ void Foam::functionObjects::histogram::writeGraph
 {
     const wordList fieldNames(1, fieldName);
 
-    fileName outputPath = baseTimeDir();
+    fileName outputPath = file_.baseTimeDir();
     mkDir(outputPath);
     OFstream graphFile
     (
@@ -75,7 +75,8 @@ Foam::functionObjects::histogram::histogram
     const dictionary& dict
 )
 :
-    writeFile(name, runTime, dict, name)
+    regionFunctionObject(name, runTime, dict),
+    file_(obr_, name)
 {
     if (!isA<fvMesh>(obr_))
     {

src/functionObjects/field/histogram/histogram.H

@@ -59,6 +59,7 @@ Usage
 
 See also
     Foam::functionObject
+    Foam::functionObjects::regionFunctionObject
     Foam::functionObjects::writeFile
 
 SourceFiles
@@ -69,8 +70,9 @@ SourceFiles
 #ifndef functionObjects_histogram_H
 #define functionObjects_histogram_H
 
-#include "writer.H"
+#include "regionFunctionObject.H"
 #include "writeFile.H"
+#include "writer.H"
 
 // * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * //
 
@@ -85,10 +87,12 @@ namespace functionObjects
 
 class histogram
 :
-    public writeFile
+    public regionFunctionObject
 {
     // Private data
 
+        writeFile file_;
+
         //- Name of field
         word fieldName_;