added ref-place and ref-transition execution support

src/main/jastadd/Navigation.jrag

@@ -95,20 +95,4 @@ aspect Navigation {
     Page contributes this
     to PetriNet.allPages()
     for petriNet();
-
-  coll java.util.Set<TransitionNode> PetriNet.allTransitionNodes() [new java.util.HashSet()] root PetriNet;
-    TransitionNode contributes this
-    to PetriNet.allTransitionNodes()
-    for petriNet();
-
-  coll java.util.Set<RefTransition> PetriNet.allRefTransitions() [new java.util.HashSet()] root PetriNet;
-    RefTransition contributes this
-    to PetriNet.allRefTransitions()
-    for petriNet();
-
-  coll java.util.Set<RefPlace> PetriNet.allRefPlaces() [new java.util.HashSet()] root PetriNet;
-    RefPlace contributes this
-    to PetriNet.allRefPlaces()
-    for petriNet();
-
 }