Lost positional attributes when saving WaterFilter.

[com.jme3.water.WaterFilter](https://github.com/jMonkeyEngine/jmonkeyengine/blob/master/jme3-effects/src/main/java/com/jme3/water/WaterFilter.java)

these 3 attributes are not saved in `public void write(JmeExporter ex)`

     //positional attributes
    private Vector3f center;
    private float radius;
    private AreaShape shapeType = AreaShape.Circular;