Fix problem with entity teleportaion

[VladoCC]

Nether portals is an absolutly random thing when it comes to teleporting of minecrats and other entities.
One time entity can be spawned at one block, other time at absoultly other side of the portal.

My suggestion for your mod is to make entities spawn at one position everytime it comes through nether portal.
As I can see your code does that for players, so it will be an good expansion for this code.