ENH: dedicated HashSetOps, HashTableOps namespaces

- relocated HashSetPlusEqOp and HashTablePlusEqOp to
  HashSetOps::plusEqOp and HashTableOps::plusEqOp, respectively

- additional functions for converting between a labelHashSet
  and a PackedBoolList or List<bool>:

  From lists selections to labelHashSet indices:

      HashSetOps::used(const PackedBoolList&);
      HashSetOps::used(const UList<bool>&);

  From labelHashSet to list forms:

      PackedBoolList bitset(const labelHashSet&);
      List<bool> bools(const labelHashSet&);

applications/utilities/postProcessing/dataConversion/foamToEnsight/findCloudFields.H

@@ -62,7 +62,7 @@ if (timeDirs.size() && !noLagrangian)
 
     if (Pstream::parRun())
     {
-        Pstream::mapCombineGather(cloudFields, HashTablePlusEqOp<word>());
+        Pstream::mapCombineGather(cloudFields, HashTableOps::plusEqOp<word>());
         Pstream::mapCombineScatter(cloudFields);
     }
 

applications/utilities/postProcessing/dataConversion/foamToEnsight/foamToEnsight.C

@@ -73,7 +73,7 @@ Note
 #include "IOmanip.H"
 #include "OFstream.H"
 #include "PstreamCombineReduceOps.H"
-#include "HashTableOps.H"
+#include "HashOps.H"
 
 #include "fvc.H"
 #include "volFields.H"

applications/utilities/postProcessing/dataConversion/foamToVTK/findClouds.H

@@ -53,7 +53,7 @@ if (timeDirs.size() && !noLagrangian)
 
     if (Pstream::parRun())
     {
-        Pstream::combineGather(allCloudDirs, HashSetPlusEqOp<word>());
+        Pstream::combineGather(allCloudDirs, HashSetOps::plusEqOp<word>());
         Pstream::combineScatter(allCloudDirs);
     }
 }

applications/utilities/postProcessing/dataConversion/foamToVTK/foamToVTK.C

@@ -147,7 +147,7 @@ Note
 #include "volPointInterpolation.H"
 #include "emptyPolyPatch.H"
 #include "PstreamCombineReduceOps.H"
-#include "HashTableOps.H"
+#include "HashOps.H"
 #include "labelIOField.H"
 #include "scalarIOField.H"
 #include "sphericalTensorIOField.H"
@@ -1482,7 +1482,7 @@ int main(int argc, char *argv[])
                     Pstream::mapCombineGather
                     (
                         cloudFields,
-                        HashSetPlusEqOp<word>()
+                        HashSetOps::plusEqOp<word>()
                     );
                     Pstream::mapCombineScatter(cloudFields);
                 }