Revert "Factor out some of the items into GameState"

This reverts commit dcfdf1c3b23f5efc93a167a599bbbbf7bf5d70d4.
Move gameEnd method to the GameRoom.

Get rid of the abstract "GameState" class--composition is better than
inheritance!
Make server messages slightly modular.

Remove the uid from all the server messages (replace with sender once we
get actors going). Start making client messages.