Implement .arena commands - add new commands to the core to handle with arena teams.

	*.arena create [player] "arena name" [type]
	*.arena create "arena name" [type]
	*.arena disband [TeamID]
	*.arena rename "oldName" "newName"
	*.arena captain [TeamID] [Player]
	*.arena info [TeamID]
	*.arena lookup [name]
Merge pull request #9842 from Bezo/Arena

Core/Command: Implement .arena commands