ENH: adjust infoSwitch to report host subscription (related to #531)

- this compact form shows the subscription per host in the unsorted
  mpi order

      nProcs : 18
      Hosts  :
      (
          (node1 6)
          (node2 8)
          (node3 4)
      )

  This provides a succinct overview of which hosts have been
  subscribed or oversubscribed.

- The longer list of "slave.pid" ... remains available on the
  InfoSwitch 'writeHosts'

etc/controlDict

@@ -38,21 +38,24 @@ InfoSwitches
     // The default ASCII write precision
     writePrecision  6;
 
-    // Enable job info
-    writeJobInfo    0;
-
     writeDictionaries 0;
     writeOptionalEntries 0;
 
     // Write lagrangian "positions" file in v1706 format (at earlier)
     writeLagrangianPositions 0;
 
-    // Report list of slaves/pids used (parallel)
-    writeSlaves     1;
+    // Report hosts used (parallel)
+    // - 0 = none
+    // - 1 = per-host-count, but unsorted
+    // - 2 = long output of "slave.pid" ...
+    writeHosts      1;
 
     // Report list of roots used (parallel)
     writeRoots      1;
 
+    // Enable job info
+    writeJobInfo    0;
+
     // Allow profiling
     allowProfiling  1;