Packets are sent out when collision happens and receiver is able to interpret and display as visual alert. Updated visual alert to looks better.

- Created yacht event code message to be sent out as packet.
- Added observers to main server thread on yacht so when collision detected, main server thread will send out yacht event message to all server to client threads.
- Updated collision visual alert using circle and animation timer.

#story[1117]

src/main/java/seng302/visualiser/GameClient.java

@@ -342,8 +342,8 @@ public class GameClient {
      * Tells race view to show a collision animation.
      */
     private void showCollisionAlert(YachtEventData yachtEventData) {
-        // 1 is used by team 28 to show collision
-        if (yachtEventData.getEventId() == 1) {
+        // 33 is the agreed code to show collision
+        if (yachtEventData.getEventId() == 33) {
             raceView.showCollision(yachtEventData.getSubjectId());
         }
     }