created listeners mechanism in three services
added updated property change event of the services
Added CRUD methods of GraphNode and GraphArc to NewGraphModel, not tested.
haven't add arcTypes  CURD.
maybe we can test new methods in NewGraphModel

possible bug:
super class DefaultGraphModel don't have fire update listeners
maybe update = delete then add again?
if it is, say we update a node
1. how to ensure the graph layout doesn't change if the text is much longer?
2. how to regenerate relationships with existing nodes, or just copy relations?