Open GUI for other users

[PimvanderLoos]

Admins should be able to open the structure GUI for other users.

We should probably have 2 modes of opening the GUI:

1. Open the GUI with the structures of another user as they would see it
   • Use the permissions+owner level of the target player.
   • Still verify any changes against the permissions+owner level of the GUI holder.
2. Open the GUI with the structures of another user, but with the permissions of the GUI holder.
   • The GUI holder will need admin bypass permissions to be able to do anything with the structures.