Updated for 2.1

A 2.1 fork of @hopefuldecay's original mod. I previously provided logic fixes for the 2.0 version, and have now completely updated the codebase to resolve the breaking prototype crashes introduced in Factorio 2.1.

As the original is currently inactive and published under the Unlicense, this version remains entirely open-source and free for anyone to modify, redistribute, or take over down the road. Enjoy!