Add a new generic graph element property for storing the reverse edge of

and edge

src/de/tudarmstadt/maki/simonstrator/api/common/graph/GenericGraphElementProperties.java

@@ -30,4 +30,5 @@ public interface GenericGraphElementProperties {
 	 */
 	public static final GraphElementProperty<Double> WEIGHT = new GraphElementProperty<>(
 			"WEIGHT", Double.class);
+	GraphElementProperty<IEdge> REVERSE_EDGE = new GraphElementProperty<IEdge>("reverseEdge", IEdge.class);
 }