Register ctkCmdLineModuleReference with the Qt metaobject system.

Libs/CommandLineModules/Core/ctkCmdLineModuleReference.h

@@ -25,6 +25,7 @@
 #include <ctkCommandLineModulesCoreExport.h>
 
 #include <QSharedDataPointer>
+#include <QMetaType>
 
 class ctkCmdLineModuleDescription;
 class ctkCmdLineModuleReferencePrivate;
@@ -58,4 +59,6 @@ private:
 
 };
 
+Q_DECLARE_METATYPE(ctkCmdLineModuleReference)
+
 #endif // CTKCMDLINEMODULEREFERENCE_H