Merge branch 'release-6.6' into 1620-monteverdi-and-mapla-segfault-at-startup

Modules/Visualization/Monteverdi/src/mvdMainWindow.cxx

...alization/MonteverdiCore/include/mvdI18nCoreApplication.h

...sualization/MonteverdiCore/include/mvdStackedLayerModel.h

...Visualization/MonteverdiCore/src/mvdStackedLayerModel.cxx

...ualization/MonteverdiGui/include/mvdLayerStackItemModel.h

...Visualization/MonteverdiGui/include/mvdLayerStackWidget.h

...sualization/MonteverdiGui/src/mvdLayerStackController.cxx

...isualization/MonteverdiGui/src/mvdLayerStackItemModel.cxx

...s/Visualization/MonteverdiGui/src/mvdLayerStackWidget.cxx

README.md