Bsworld files: Importing/exporting worlds

[Qwertygiy]

Now that we have multiple worlds, I think it would be a good idea to be able to export worlds from one game and import them into another like we can models. I expect it wouldn't be too different from the old .buildism files, and I know I would be able to use it for Buildismaran -- and if that becomes a community project then it would definitely be a huge advantage.