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.

applications/utilities/postProcessing/noise/noise.C

@@ -81,7 +81,6 @@ See also
 #include "noiseFFT.H"
 #include "argList.H"
 #include "Time.H"
-#include "writeFiles.H"
 #include "CSV.H"
 
 // * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * //