Deadly End Phantoms

Added the End Phantom!

They spawn instead of vanilla phantoms in the End, are not undead and pursue flying players relentlessly.

The texture came from here, and I got the permission of the artist to use it in the mod: https://www.reddit.com/r/Minecraft/comments/83wo3s/phantom_retexture_download_link_in_comments/

There is also a config option to disable natural vanilla phantom spawns in the overworld.