Add Rectangle Shape or ability to set Max/min X and Z seperately.

[Toritos]

Issue Type: Not an issue but a feature request. Could there be an option to use Max X/Max Z and Min X/Min Z to define the area where rtp can take you? It would be useful for worlds with rectangular world borders!

[SuperRonanCraft]

I would like this as a feature, there is already a lot of configuration and I don't want to complicate the config file even more, but I will add this as an optional feature ;)