Created annotation slider to display different levels of annotations

Removed toggleAnnotations method as abstract from race object and made only for boat group as it didnt make sense for markgroup, at least not currently as they have no annotations to show

#story[558]

src/main/java/seng302/models/RaceObject.java

@@ -76,6 +76,4 @@ public abstract class RaceObject extends Group {
     public abstract boolean hasRaceId (int... raceIds);
 
     public abstract int[] getRaceIds ();
-
-    public abstract void toggleAnnotations ();
 }