fix bugs, ready lab 6

ProjectElectricLocomotive/LocomotiveGenericCollection.java

@@ -91,4 +91,8 @@ public class LocomotiveGenericCollection<T extends DrawingLocomotive,U extends I
             i++;
         }
     }
+
+    public void clear() {
+        _collection.clear();
+    }
 }

ProjectElectricLocomotive/LocomotivesGenericStorage.java

@@ -96,7 +96,7 @@ public class LocomotivesGenericStorage {
             LocomotiveGenericCollection<DrawingLocomotive, DrawingObjectLocomotive> collection;
             if (_locomotiveStorage.containsKey(key)){
                 collection = _locomotiveStorage.get(key);
-//                collection.clear();  // what is the wtf???
+                collection.clear();
             }
             else
                 collection = new LocomotiveGenericCollection<>(_pictureWidth, _pictureHeight);

ProjectElectricLocomotive/SetGeneric.java

@@ -66,4 +66,7 @@ public class SetGeneric<T extends DrawingLocomotive>{
         return _places;
     }
 
+    public void clear() {
+        _places.clear();
+    }
 }