Commands:
/duel <Player_name> - [Command aliases: /challenge]
/duelreqs - [Command aliases: /duelrequests]
/accept <Player_name> - [Command aliases: /duelaccept]
/reject <Player_name> - [Command aliases: /deny, /duelreject, /dueldeny]
/duelclear - [Command aliases: /duelremove]