BulletSim: add osGetPhysicsEngineType() LSL function and update

the physics engines to return the name that is specified in the INI
file ("physics = XXX") as the type of engine.
This os function is a little different than the others in that it
does not throw an exception of one is not privilaged to use it.
It merely returns an empty string.

OpenSim/Region/Physics/OdePlugin/OdePlugin.cs

@@ -72,7 +72,7 @@ namespace OpenSim.Region.Physics.OdePlugin
                 // http://opensimulator.org/mantis/view.php?id=2750).
                 d.InitODE();
                 
-                m_scene = new OdeScene(sceneIdentifier);
+                m_scene = new OdeScene(GetName(), sceneIdentifier);
             }
 
             return m_scene;