Add a server-sided way to remove color codes from incoming chat messages (#5948)

These code be generated by CSM, a modded client or just copy and pasted by the player.

Changes
- Update configuration example and setting translation file.
- Remove colour codes before logging chat.
- Add setting to remove colour codes before processing the chat.

src/server.h

@@ -488,7 +488,7 @@ private:
 
 	// This returns the answer to the sender of wmessage, or "" if there is none
 	std::wstring handleChat(const std::string &name, const std::wstring &wname,
-		const std::wstring &wmessage,
+		std::wstring wmessage_input,
 		bool check_shout_priv = false,
 		RemotePlayer *player = NULL);
 	void handleAdminChat(const ChatEventChat *evt);