Fix mobs not passing through portals correctly.

This fixes so that mobs going through a portal don't end up in stock "End" or "Nether".
But instead its assigned world.

Plus cleaned up some unused codes.

Uploaded a compiled jar for people to test and confirm.
https://www.dropbox.com/s/dg93pxj6saogm99/NWorld.jar

Or you can always compile it yourself, incase you dont trust third party.