Introduced the TeleportRequest class to store the details of a teleport request (important for differentiating between a /tpa and /tpahere request).
Added an Overwrite logic which only lets a player have one outgoing request to their target, rather than being able to stack infinite teleport requests to the same target. This applies to both /tpa and /tpahere
Added a check which doesn't allow a player to send a teleport request to themselves.