ENH: Add ability to set heavy data writer in writer after initialization.

Add setter to writer to set heavy data writer.

core/XdmfWriter.cpp

@@ -227,6 +227,12 @@ XdmfWriter::setDocumentTitle(std::string title)
   mImpl->mDocumentTitle = title;
 }
 
+void 
+XdmfWriter::setHeavyDataWriter(shared_ptr<XdmfHeavyDataWriter> heavyDataWriter)
+{
+  mImpl->mHeavyDataWriter = heavyDataWriter;
+}
+
 void
 XdmfWriter::setLightDataLimit(const unsigned int numValues)
 {

core/XdmfWriter.hpp

@@ -148,6 +148,14 @@ public:
    */
   bool getWriteXPaths() const;
 
+  /**
+   * Set the heavy data writer that this XdmfWriter uses to write
+   * heavy data to disk.
+   *
+   * @param heavyDataWriter the heavy data writer to set.
+   */
+  void setHeavyDataWriter(shared_ptr<XdmfHeavyDataWriter> heavyDataWriter);
+
   /**
    * Set the number of values that this writer writes to light data
    * (XML) before switching to a heavy data format.