Fixed some issues around display names and friends; Implemented worlds

There were a whole lot of issues around display names and friends, of which most *should* be fixed now. 
Also, it should now be possible to see a friend as "online" if they're logged in and have the appropriate online status (friends only should mean only visible to people on their friends list, whereas "everyone" should mean visible to all).
Private messaging has not yet been implemented. I need some packets identified for them, first. Not sure whether it's better to finish the lobby or to move onto the game itself, though...