Deletion of an object from a derived layer should be disallowed in the UI

[bctcvai]

Deletion of an object from a derived layer should be disallowed in the UI.

"if I edit the localization, and then delete it on my layer, then you end up in a state where the "original" object shows up again" --> Correct behavior

"but if you delete that object (when a derived layer is selected), it's gone in the base layer" --> Bad behavior