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.

src/osgParticle/ParticleSystemUpdater.cpp

@@ -32,7 +32,7 @@ void osgParticle::ParticleSystemUpdater::traverse(osg::NodeVisitor& nv)
             {
                 _frameNumber = nv.getFrameStamp()->getFrameNumber();
 
-                double t = nv.getFrameStamp()->getReferenceTime();
+                double t = nv.getFrameStamp()->getSimulationTime();
                 if (_t0 != -1.0)
                 {
                     ParticleSystem_Vector::iterator i;