[idea] Replace destroyer with restrictor

[Emxx52]

Destroyer is in the game because we've got the source code for CeeBot-Teen along with Colobot. We've just put it there because we had an empty slot. It's not supposed to be buildable in the story campaign, and we might replace it with something else in the future. And yes, the buiding seems utterly useless outside of CeeBot-Teen.

I couldn't be more delighted with your use of Combine/Overwatch Thumper/Restrictor as an inspiration, as I am a huge Lambda fan myself, but adding new buildings to Colobot: Gold Edition is rather out of the question (except for some BuzzingCars and BlupiMania-2 stuff of course, and that's slowly being integrated into the main game right now).