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.

include/osg/FrameStamp

@@ -46,6 +46,9 @@ class OSG_EXPORT FrameStamp : public Referenced
         void setReferenceTime(double refTime) { _referenceTime = refTime; }
         double getReferenceTime() const { return _referenceTime; }
         
+        void setSimulationTime(double refTime) { _simulationTime = refTime; }
+        double getSimulationTime() const { return _simulationTime; }
+        
         void setCalendarTime(const tm& calendarTime);
         void getCalendarTime(tm& calendarTime) const;
 
@@ -62,7 +65,7 @@ class OSG_EXPORT FrameStamp : public Referenced
     
         int     _frameNumber;
         double  _referenceTime;
-        
+        double  _simulationTime;        
         
         // member variables of time.h's tm structure, copied here to
         // ensure that all data is not dynamic. The tm structure itself