Fix tp snipe simple

[oversword]

Resurrects #48
Undoes #50
Choose between this and #49

(Attempts) to fix the TP sniping issue / the issue with unexpected behaviour
Fixes BlockySurvival/issue-tracker#83
Fixes BlockySurvival/issue-tracker#320

The fix here attempts to allow only one request per user at any time, to avoid any conflicts with multiple requests

These changes definitely need some consideration and testing, I'm unsure if they actually "fix" the problem, I have just attempted to prevent it from happening in the first place.

This the is "simple" solution, I conceived of a more complex solution based on the discussions in BlockySurvival/issue-tracker#83 , but decided to implement this one first as it was faster to write.

• These changes may make the mod unpleasant to use, it may feel like it's constantly telling you it's not working
• This only works if the lists are correctly cleared, something which is not guaranteed, but I may have only seen this happening in the the previous broken states
• We might also want to send a message to the receiver telling them someone attempted to make another request so they can talk to them after they have cleared their current request

[Panquesito7]

I believe #49 is a better option: way cleaner and adds more features, IMO.
Will be closing this PR for now. Still, thanks for your efforts and contributions. 🙂