0.7.16 released

Add a mechanism to open a dialog from the MDIApplication. This allows for example to open only one instance of a dialog without having to define it as modal
Add a new MDIDialogHelper interface and the associated default implementation to handle opening dialogs
Make the AbstractMDIMenuFactory derive from the new MDIMenuFactory interface. The GUIApplication now does not depend anymore directly on the abstract implementation
Breaking change: The createPopupMenu method in the AbstractMDIMenuFactory becomes a public method