Added osg::FrameStamp::set/getSimulationTime().

Added setting of osg_SimulationTime and osg_DeltaSimulationTime to the uniforms set by SceneView

Added frame(double simulationTime) and advance(double simulationTime) parameters to
osgViewer::SimpleViewer, Vewer and CompositeViewer.

Updated various examples and Nodes to use SimulationTime where appropriate.

examples/osgfxbrowser/osgfxbrowser.cpp

@@ -34,7 +34,7 @@ public:
     {
         osg::MatrixTransform *xform = dynamic_cast<osg::MatrixTransform *>(node);
         if (xform && enabled_) {
-            double t = nv->getFrameStamp()->getReferenceTime();
+            double t = nv->getFrameStamp()->getSimulationTime();
             xform->setMatrix(osg::Matrix::rotate(t, osg::Vec3(0, 0, 1)));
         }
         traverse(node, nv);