AmkMcAuth

Bug fix:
When a server uses the multiverse plugin and a world is removed,
has "teleport to spawn" on and a player playing on that removed world
joins the server AmkMcAuth gives crashes while it tries to teleport the player to spawn
becaus that spoinpoint is no langer there (no world).
Now AmkMcAuth does nothing and let Spigot handle this situation.

New functionality:
Players in process of loggin (not logged in yet) can now be set invisible for other player.
AmkMcAuth can now execute console command when players Join, Logon Logout or Leave.