Function used in mission creation.

Represents a disc in wich entities can be teleported.
Entities are teleported on a random point within the zone.

name : name of the zone. 2 ZONES CANNOT SHARE THE SAME NAME.

radius : radius of the delimiting circle in meter

use_z : if checked, the z property will be used

z : z cords of the disc

Angle : heading of entities after teleportation