Improved TabList behaviour:
* Players can be hidden from each other on the tab list
  * Players can have tab groups, only players that can see all the tab groups a player is part of can see the player in the tab list
  * To assign a player to a group, set the property "TL:group:<group>" = true
  * To allow a player to see a group, set the property "TL:see:<group>" = true
  * To allow a player to see everyone, set the property "TL:seeall" = true