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/Manager/PhysicsScene.cs

@@ -62,13 +62,20 @@ namespace OpenSim.Region.Physics.Manager
 //        private static readonly ILog m_log = LogManager.GetLogger(MethodBase.GetCurrentMethod().DeclaringType);
 
         /// <summary>
-        /// Name of this scene.  Useful in debug messages to distinguish one OdeScene instance from another.
+        /// A unique identifying string for this instance of the physics engine.
+        /// Useful in debug messages to distinguish one OdeScene instance from another.
+        /// Usually set to include the region name that the physics engine is acting for.
         /// </summary>
         public string Name { get; protected set; }
 
+        /// <summary>
+        /// A string identifying the family of this physics engine. Most common values returned
+        /// are "OpenDynamicsEngine" and "BulletSim" but others are possible.
+        /// </summary>
+        public string EngineType { get; protected set; }
+
         // The only thing that should register for this event is the SceneGraph
         // Anything else could cause problems.
-
         public event physicsCrash OnPhysicsCrash;
 
         public static PhysicsScene Null