Duplicate association end names should not be created

[Jörg Kienzle]

When one creates two associations between the same two classes, the default association end names are the same. This, of course, then raises a validation error.

[Jörg Kienzle]

Resolved Issue #188

Now, the default association end name is set to <"my" + target class name>. If that name is already taken, it tries <"my" + target class name + a numerically increasing number> until it finds one that is not used

→ <<cset 77dee4cb9457>>