Server now stores all the lines that have been drawn on the canvas and sends them to new players. When all players have left the game, the canvas is cleared.

Client only draws received canvas data if they have actually joined the game.
Client will now get the proper "lost connection" overlay when unexpectedly losing connection to the server.
Added an optional argument to the server's log function. This argument takes a global.LOGTYPE enum value (defined in shared/constants.js). Based on what log type is specified, the log message will be displayed differently.
Removed old code.