Added name fields to Collision Object and Shape.

Added name field to Typed Constraint.
Added accessor for gravity in dynamics world.

src/BulletDynamics/Dynamics/btSimpleDynamicsWorld.cpp

@@ -121,6 +121,11 @@ void	btSimpleDynamicsWorld::setGravity(const btVector3& gravity)
 	}
 }
 
+btVector3 btSimpleDynamicsWorld::getGravity () const
+{
+	return m_gravity;
+}
+
 void	btSimpleDynamicsWorld::removeRigidBody(btRigidBody* body)
 {
 	removeCollisionObject(body);