The current situation of throw-every-piece-of-logic-into-one-file for each
server isn't working out. So now there is a new ZoneConnection/LobbyConnection
struct that will be delegating tasks to their own Handlers (for example, there
could be a ChatHandler.)
I'm not sure how well this architecture will scale, but it's better than what
we have right now.
It's a hack and only really works going from New -> Old Gridania, but this does
work! It also means Kawari now actually requires a valid game installation,
since it has to read layer group information.
