Add "In Diagram" info on the Traceability view

[Guillaume]

The Traceability view is useful to check all linked elements from the selected one e.g. a class and its associated classes.
This view can be used as an alternative to the Insert Related Elements to add linked elements on the active diagram.

It would be useful to have visibilty on whether a linked elements on the traceability view is in the current diagram (unless there's no active diagram), similarly to the In Diagram (Yes/No) column info on the Insert Related Elements window.