ENH: improved sample surfaces and surface writers (#1206)

- The writers have changed from being a generic state-less set of
  routines to more properly conforming to the normal notion of a writer.
  These changes allow us to combine output fields (eg, in a single
  VTK/vtp file for each timestep).

  Parallel data reduction and any associated bookkeeping is now part
  of the surface writers.
  This improves their re-usability and avoids unnecessary
  and premature data reduction at the sampling stage.

  It is now possible to have different output formats on a per-surface
  basis.

- A new feature of the surface sampling is the ability to "store" the
  sampled surfaces and fields onto a registry for reuse by other
  function objects.

  Additionally, the "store" can be triggered at the execution phase
  as well

src/functionObjects/field/fieldValues/surfaceFieldValue/surfaceFieldValue.C

@@ -953,20 +953,23 @@ bool Foam::functionObjects::fieldValues::surfaceFieldValue::read
     {
         const word formatName(dict.get<word>("surfaceFormat"));
 
-        if (formatName != "none")
-        {
-            surfaceWriterPtr_.reset
+        surfaceWriterPtr_.reset
+        (
+            surfaceWriter::New
             (
-                surfaceWriter::New
-                (
-                    formatName,
-                    dict.subOrEmptyDict("formatOptions")
-                        .subOrEmptyDict(formatName)
-                )
-            );
+                formatName,
+                dict.subOrEmptyDict("formatOptions").subOrEmptyDict(formatName)
+            )
+        );
 
+        if (surfaceWriterPtr_->enabled())
+        {
             Info<< "    surfaceFormat = " << formatName << nl;
         }
+        else
+        {
+            surfaceWriterPtr_->clear();
+        }
     }
 
     Info<< nl << endl;