PortalStructure now contains information about the gate's physical structure, such as the location of border blocks, the location of entrances, the gate type and the button location.
PortalActivator is responsible for activating/de-activating portals, destination toggling and getting information about available destinations.
PortalOpener is responsible for opening/closing a portal. It's also the place to go for checking if the portal is open for a given player.
Comments of the Portal class have been improved, but the comments of the three new classes need fixing.
Moves player-related teleportation code to PlayerTeleporter, moves vehicle-related teleportation code to VehicleTeleporter and makes them both extend the Teleporter which now contains all common teleportation code.
Adds a proper permission check to make sure players are allowed to teleport through the artificial portal
Adds a teleportation back to the entrance as the teleportation event cannot be properly cancelled
Adds a proper class for storing info about the teleportation
