- Instead, ensure that DiagramEditorBase has the focus when a child edit part is added or removed
- This works around #2207 and also the same part of #1491 as with the old workaround
- Summing up:
   - Undo/redo of operations on the model only works if either the NavigatorViewPart or a DiagramEditorBase has the focus
   - This makes sense if the active view provides editable items itself (e.g., the GenericAnnotationView) *and* provides undo/redo (currently not the case for GenericAnnotationView).
   - For other (read-only) view (e.g., Model Markers), this behavior is confusing for the user
refs 2207,1491