BUG: collated ensight not working with isosurfaces (closes #318)

- the problem arises since the various surface writers are stateless.
  The collated output format hacks around this limitation by adding in
  its own fieldDict caching (to disk).

  Now include an updateMesh() method to hook into geometry changes.
  This is considered a stop-gap measure until the surface output
  handling is improved.

src/fileFormats/ensight/file/ensightCase.C

@@ -138,7 +138,7 @@ Foam::scalar Foam::ensightCase::writeTimeset() const
 {
     const label ts = 1;
 
-    const labelList indices = timesUsed_.sortedToc();
+    const labelList indices(timesUsed_.sortedToc());
     label count = indices.size();
 
     // correct for negative starting values

src/fileFormats/ensight/file/ensightCase.H

@@ -106,7 +106,7 @@ private:
         //- Record time indices when geometry is written.
         //  These values will be used to decide if timeset 1
         //  or a separate timeset are used.
-        //  The special index '-1' is used static geometry.
+        //  The special index '-1' is used for static geometry.
         mutable labelHashSet geomTimes_;
 
         //- Record time indices when clouds are written.