WhiteRabbit: create plugin

A "Secret Door" is a custom item. When placed, it appears and functions mostly like a vanilla iron door. However, if reinforced, the door only ever opens from the perspective of players on the group. To a player who is not on the group, the door would appear to never open, even if it actually is open. If a player who is on the group opens it, an outsider would see that player appear to phase through a closed door.