[P3] Deduplicate functions in Game and SP code

Nearly every function is server/game.coffee is duplicated in server/single_player.coffee:

dnsHealthCheck = () ->
server = http.createServer (req, res) ->
server.listen config.get('game_port'), () ->
savePlayerCount = (playerCount) ->
saveGameCount = (gameCount) ->
getConnectedSpectatorsDataForGamePlayer = (gameId,playerId)->
onGamePlayerJoin = (requestData) ->
onGameSpectatorJoin = (requestData) ->
onGameLeave = (requestData) ->
onGameEvent = (eventData) ->
onGameDisconnect = () ->
playerLeaveGameIfNeeded = (socket, silent=false) ->
spectatorLeaveGameIfNeeded = (socket) ->
destroyGameSessionIfNoConnectionsLeft = (gameId,persist=false)->
tearDownSpectateSystemsIfNoSpectatorsLeft = (gameId)->
clearDisconnectedPlayerTimeout = (gameId) ->
startDisconnectedPlayerTimeout = (gameId,playerId) ->
onDisconnectedPlayerTimeout = (gameId,playerId) ->
restartTurnTimer = (gameId) ->
stopTurnTimer = (gameId) ->
onGameTimeTick = (gameId) ->
restartSpectatorDelayedGameInterval = (gameId) ->
stopSpectatorDelayedGameInterval = (gameId) ->
onSpectatorDelayedGameTick = (gameId) ->
flushSpectatorNetworkEventBuffer = (gameId) ->
_logSpectatorTickInfo = _.debounce((gameId)->
emitGameEvent = (fromSocket,gameId,eventData)->
initGameSession = (gameId,onComplete) ->
initSpectatorGameSession = (gameId)->
onBeforeRollbackToSnapshot = (event) ->
onStep = (event) ->
onInvalidAction = (event) ->
subscribeToGameSessionEvents = (gameId)->
unsubscribeFromGameSessionEvents = (gameId)->
afterGameOver = (gameId, gameSession, mouseAndUIEvents) ->
shutdown = () ->

We should deduplicate as much of this as possible to make maintenance easier.