Allow customization of /list output

[Bobcat00]

When a player has a nickname, the output of the /list command includes the player's real name in parenthesis, in white. However, that cannot be customized to use different colors or for that matter something other than parentheses. The format appears to be hardcoded in PlayerList#listUsers.

I suggest the (playername) part be customizable like the rest of the message.

[JRoy]

Added in e4cf965