Made a couple of fixes including bugs in the leader board…

• Updated the leaderboard so that it no longer shows players that are connected but do not have a ship assigned. This was resulting in blank positions on the leaderboard.
• Updated the game engine to include the thruster animations in the server updates. So now, players see thruster animations for all ships, not just their own.
• Updated the game engine so that ships are removed from play when a player disconnects. This way, players can not spam new ships onto the map.