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/mark/MarkGroup.java

@@ -223,9 +223,6 @@ public class MarkGroup extends RaceObject {
                 return true;
         return false;
     }
-    public void toggleAnnotations () {
-
-    }
 
     public static int getMarkRadius() {
         return MARK_RADIUS;