REQUEST - Introduce ability to enable worlds that use the plugin

PocketMine-MP version 1.6.2dev "Unleashed" (API 3.0.0-ALPHA3)
PHP 7.0.15

Hi great plugin! i am using it on my home server for the kids.

i have an issue with the plugin when playing minigames as i do not wish to use it in these worlds.

if possible could i ask that you think about introducing a world enabled list in the config.yml

Kind Regards
Star

