- after renaming a message, we need to undo twice to undo the renaming (there are two "Message Update" commands to undo) 
	=> Bug 395439 - XText MessagePopupEditor creates two identical commands
- Bug 395485 - XText validation error when clicking while XText editor is opening
- Bug 395490 - SelectByTypeHandler fails when Views with no semantic element are present
- Bug 395800 - NPE in UnloadHandler with notational-only Views
- when resizing an interaction or adding a lifeline or more state definitions, existing lifelines get smaller and some of their contents (time elements, general orderings and labels) may get hidden
	=> automatically move contents back inside the Lifelines?
	   or automatically enlarge the Interaction to make all contents fit?