Added ability to alter the verbosity of the notify messages with the

running of osgTerrain::DataSet via a static s/getNotifyOffset(int) method.

examples/osgsimulation/osgsimulation.cpp

@@ -26,7 +26,6 @@ class GraphicsContext {
             rs->useBorder(false);
             rs->useConfigEventThread(false);
             rs->realize();
-            std::cout<<"Realized window"<<std::endl;
         }
 
         virtual ~GraphicsContext()
@@ -44,6 +43,9 @@ osg::Node* createEarth()
     {
         std::string filename = osgDB::findDataFile("Images/land_shallow_topo_2048.jpg");
 
+        // make osgTerrain::DataSet quieter..
+        osgTerrain::DataSet::setNotifyOffset(1);
+
         osg::ref_ptr<osgTerrain::DataSet> dataSet = new osgTerrain::DataSet;
 
         // register the source imagery