BUG: Add ConstantImageFilter::DynamicThreadedGenerateData

Detected by:

  include/itkMetamorphosisImageRegistrationMethodv4.h:74:8: warning: 'ThreadedGenerateData' overrides a member function but is not marked 'override' [-Winconsistent-missing-override]

ThreadedGenerateData has been replace by DynamicThreadedGenerateData in
ITK 5:

  https://github.com/InsightSoftwareConsortium/ITK/blob/master/Documentation/ITK5MigrationGuide.md

include/itkMetamorphosisImageRegistrationMethodv4.h

@@ -71,17 +71,15 @@ public ImageToImageFilter<TInputImage, TOutputImage>
   ~ConstantImageFilter(){}
 
   /** Does the real work. */
-  void ThreadedGenerateData(  const typename OutputImageType::RegionType& outputRegionForThread, ThreadIdType threadId)
+  void DynamicThreadedGenerateData(const typename OutputImageType::RegionType& outputRegionForThread) override
   {
-    ProgressReporter progress(this, threadId, outputRegionForThread.GetNumberOfPixels());
     OutputPixelType constant = this->GetConstant();
     OutputImageIteratorType  it(this->GetOutput(),outputRegionForThread);
 
     while(!it.IsAtEnd())
     {
       it.Set(constant);
       ++it;
-      progress.CompletedPixel();
     }
   }