Added osgUtil::CullVisitor::getCurentRenderGraph() and getRootRenderGraph()

methods which replace getRenderGraph(). Small changing of order of push/pop
of StateSet's in SceneView to clean things up.

include/osgUtil/CullVisitor

@@ -185,11 +185,16 @@ class OSGUTIL_EXPORT CullVisitor : public osg::NodeVisitor
             _currentRenderGraph = rg;
         }
 
-        inline RenderGraph* getRenderGraph()
+        inline RenderGraph* getRootRenderGraph()
         {
             return _rootRenderGraph.get();
         }
 
+        inline RenderGraph* getCurrentRenderGraph()
+        {
+            return _currentRenderGraph;
+        }
+
         inline void setRenderStage(RenderStage* rg)
         {
             _rootRenderStage = rg;