Debug console

I’ve added a debug console that can be opened from inside Yollicosmic. It wraps its input in a (semi-) sandboxed function environment so that I can make anything I need to available without the console getting free access to everything in the Lua global space.

Right now, there’s not a whole lot to do with it, but it was a fun side project to add, and it might be useful in the future. It can be enabled at startup with a flag in the global options.