controlDict: the optional graphFormat entry is now used as the default for all setFormat entries

Foam::graph superseded by the more general Foam::setWriter reducing code
maintenance overhead, simplifying usage and further development.

applications/utilities/postProcessing/lagrangian/particleTracks/createFields.H

@@ -6,4 +6,7 @@ label sampleFrequency(propsDict.lookup<label>("sampleFrequency"));
 
 label maxPositions(propsDict.lookup<label>("maxPositions"));
 
-word setFormat(propsDict.lookupOrDefault<word>("setFormat", "vtk"));
+word setFormat
+(
+    propsDict.lookupOrDefault<word>("setFormat", runTime.graphFormat())
+);