fieldAverage: Name the field averaging properties file "<functionObject name>Properties"

rather than the fixed name "fieldAveragingProperties" to allow for the
same field to be averaged more than once.

Resolves bug-report http://www.openfoam.org/mantisbt/view.php?id=1336

src/postProcessing/functionObjects/field/fieldAverage/fieldAverage/fieldAverage.C

@@ -186,7 +186,7 @@ void Foam::fieldAverage::writeAveragingProperties() const
     (
         IOobject
         (
-            "fieldAveragingProperties",
+            name() + "Properties",
             obr_.time().timeName(),
             "uniform",
             obr_,
@@ -225,7 +225,7 @@ void Foam::fieldAverage::readAveragingProperties()
     {
         IOobject propsDictHeader
         (
-            "fieldAveragingProperties",
+            name() + "Properties",
             obr_.time().timeName(obr_.time().startTime().value()),
             "uniform",
             obr_,