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.
leaving it up to the Viewer to specify the mode (which by default is MultiThreaded).
Added a check for the presence of osgParticle systems so that threading is
disabled in this case.
hardware generate mip mapping.
Added switching off generate mip map from osgText::Font.cpp.
Changed savedmodel.osg to saved_model.osg in ViewerEventHandler.