build 20080616

The first Delete key removes the link label, the 2nd Delete key prompts to delete the link.
- create a class diagram
- create and name 2 classes "A" and "B"
- create a navigable aggregation (association or composition) between the 2 classes
- delete the navigable link from the diagram only, not from model
- click on Discover Relationship button on the toolbar
Result: the recovered link is shown as a regular association link, even though the properties window still shows as
navigable link. See attached screenshot.