Mychunk reloaded

Added /mc tp <player> (or /chunk tp <player>) to teleport to someone's chunk. Permission: mychunk.comand.teleport

Big performance iprovement, the plugin was using an "on any move event", wich is very, very laggy.

By the way, removed the feature wich said you that a chunk was for sale, but when it takes so much RAM, we must make some concessions.

Improved access for admins: the permission "mychunk.override" is now a real override permission.