Merge branch 'add-ctklayoutviewfactory' into atlas-viewer-slicer-4.3

* add-ctklayoutviewfactory:
  Separate viewFromXML to createViewFromXML
  Add ctkLayoutFactory and ctkLayoutViewFactory
Add documentation for ctk*PopupWidget
Merge branch 'add-popup-documentation'

* add-popup-documentation:
  Add documentation for ctk*PopupWidget