Duplicate fixture remover no longer as useful

[kingjon3377]

One of the main features of the "duplicate fixture remover" app was to coalesce animals and resource piles inside units and fixtures. Since the refactoring to move mutating operations into driver models, that apparently no longer works, though the user is presented with repeated prompts for the same kind of animal (e.g.), sometimes for units that I don't remember containing any animals. If it does actually work I can't see how it can.