Fix windows build errors related to relocation of classes

This commit update the export macro according to accommodate the
relocation of the classes done in commit 448aaf3

Error were similar to the report below:

.\moc_ctkHistogram.cxx(40) : error C2491: 'ctkHistogram::staticMetaObject' : definition of dllimport static data member not allowed

Libs/Visualization/VTK/Widgets/ctkVTKColorTransferFunction.h

@@ -24,17 +24,17 @@
 // CTK includes
 #include "ctkTransferFunction.h"
 #include "ctkPimpl.h"
-#include "ctkVisualizationVTKCoreExport.h"
+#include "ctkVisualizationVTKWidgetsExport.h"
 #include "ctkVTKObject.h"
 
 class vtkColorTransferFunction;
 class ctkVTKColorTransferFunctionPrivate;
 
-/// \ingroup Visualization_VTK_Core
+/// \ingroup Visualization_VTK_Widgets
 ///
 /// Transfer function for a vtkColorTransferFunction. 
 /// The value is an RGB QColor (no alpha supported)
-class CTK_VISUALIZATION_VTK_CORE_EXPORT ctkVTKColorTransferFunction: public ctkTransferFunction
+class CTK_VISUALIZATION_VTK_WIDGETS_EXPORT ctkVTKColorTransferFunction: public ctkTransferFunction
 {
   Q_OBJECT;
   QVTK_OBJECT;

Libs/Visualization/VTK/Widgets/ctkVTKCompositeFunction.h

@@ -24,18 +24,18 @@
 // CTK includes
 #include "ctkTransferFunction.h"
 #include "ctkPimpl.h"
-#include "ctkVisualizationVTKCoreExport.h"
+#include "ctkVisualizationVTKWidgetsExport.h"
 #include "ctkVTKObject.h"
 
 class vtkPiecewiseFunction;
 class vtkColorTransferFunction;
 class ctkVTKCompositeFunctionPrivate;
 
-/// \ingroup Visualization_VTK_Core
+/// \ingroup Visualization_VTK_Widgets
 ///
 /// Transfer function for a vtkPiecewiseFunction
 
-class CTK_VISUALIZATION_VTK_CORE_EXPORT ctkVTKCompositeFunction: public ctkTransferFunction
+class CTK_VISUALIZATION_VTK_WIDGETS_EXPORT ctkVTKCompositeFunction: public ctkTransferFunction
 {
   Q_OBJECT;
   QVTK_OBJECT;

Libs/Visualization/VTK/Widgets/ctkVTKHistogram.h

@@ -24,17 +24,17 @@
 // CTK includes
 #include "ctkHistogram.h"
 #include "ctkPimpl.h"
-#include "ctkVisualizationVTKCoreExport.h"
+#include "ctkVisualizationVTKWidgetsExport.h"
 #include "ctkVTKObject.h"
 
 class vtkDataArray;
 class ctkVTKHistogramPrivate;
 
-/// \ingroup Visualization_VTK_Core
+/// \ingroup Visualization_VTK_Widgets
 ///
 /// Transfer function for a vtkColorTransferFunction. 
 /// The value is an RGB QColor (no alpha supported)
-class CTK_VISUALIZATION_VTK_CORE_EXPORT ctkVTKHistogram: public ctkHistogram
+class CTK_VISUALIZATION_VTK_WIDGETS_EXPORT ctkVTKHistogram: public ctkHistogram
 {
   Q_OBJECT;
   QVTK_OBJECT;

Libs/Visualization/VTK/Widgets/ctkVTKLookupTable.h

@@ -24,17 +24,17 @@
 // CTK includes
 #include "ctkTransferFunction.h"
 #include "ctkPimpl.h"
-#include "ctkVisualizationVTKCoreExport.h"
+#include "ctkVisualizationVTKWidgetsExport.h"
 #include "ctkVTKObject.h"
 
 class vtkLookupTable;
 class ctkVTKLookupTablePrivate;
 
-/// \ingroup Visualization_VTK_Core
+/// \ingroup Visualization_VTK_Widgets
 ///
 /// Transfer function for a vtkColorTransferFunction. 
 /// The value is an RGB QColor (no alpha supported)
-class CTK_VISUALIZATION_VTK_CORE_EXPORT ctkVTKLookupTable: public ctkTransferFunction
+class CTK_VISUALIZATION_VTK_WIDGETS_EXPORT ctkVTKLookupTable: public ctkTransferFunction
 {
   Q_OBJECT;
   QVTK_OBJECT;

Libs/Visualization/VTK/Widgets/ctkVTKPiecewiseFunction.h

@@ -24,17 +24,17 @@
 // CTK includes
 #include "ctkTransferFunction.h"
 #include "ctkPimpl.h"
-#include "ctkVisualizationVTKCoreExport.h"
+#include "ctkVisualizationVTKWidgetsExport.h"
 #include "ctkVTKObject.h"
 
 class vtkPiecewiseFunction;
 class ctkVTKPiecewiseFunctionPrivate;
 
-/// \ingroup Visualization_VTK_Core
+/// \ingroup Visualization_VTK_Widgets
 ///
 /// Transfer function for a vtkPiecewiseFunction
 
-class CTK_VISUALIZATION_VTK_CORE_EXPORT ctkVTKPiecewiseFunction: public ctkTransferFunction
+class CTK_VISUALIZATION_VTK_WIDGETS_EXPORT ctkVTKPiecewiseFunction: public ctkTransferFunction
 {
   Q_OBJECT;
   QVTK_OBJECT;

Libs/Widgets/ctkHistogram.h

@@ -30,18 +30,18 @@
 
 /// CTK includes
 #include "ctkTransferFunction.h"
-#include "ctkCoreExport.h"
+#include "ctkWidgetsExport.h"
 
 //-----------------------------------------------------------------------------
-/// \ingroup Core
-struct CTK_CORE_EXPORT ctkHistogramBar : public ctkControlPoint
+/// \ingroup Widgets
+struct CTK_WIDGETS_EXPORT ctkHistogramBar : public ctkControlPoint
 {
   QColor Color;
 };
 
 //-----------------------------------------------------------------------------
-/// \ingroup Core
-class CTK_CORE_EXPORT ctkHistogram: public ctkTransferFunction
+/// \ingroup Widgets
+class CTK_WIDGETS_EXPORT ctkHistogram: public ctkTransferFunction
 {
   Q_OBJECT
 public: