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/osg/FrameStamp.cpp

@@ -18,6 +18,7 @@ FrameStamp::FrameStamp():Referenced()
 {
     _frameNumber=0;
     _referenceTime=0;
+    _simulationTime=0;
 
     tm_sec=0;            /* Seconds.        [0-60] (1 leap second) */
     tm_min=0;            /* Minutes.        [0-59] */