Adding rg in the left tree

src/ui/GTURTLEModeling.java

src/ui/InvariantSynchro.java

src/ui/JMenuBarTurtle.java

src/ui/MainGUI.java

src/ui/graph/AUTGraph.java

src/ui/graph/RG.java

src/ui/tree/DiagramTreeModel.java

src/ui/tree/DiagramTreeRenderer.java

src/ui/tree/GraphTree.java

src/ui/tree/JDiagramTree.java

src/ui/tree/ValidationDataTree.java

src/ui/window/JDialogAvatarModelChecker.java