add improved btGeneric6DofSpring2Constraint, thanks to Puhr Gabor and Tamas Umenhoffer!

improved the new demo testbed (work-in-progress)
add basic Lua demo, import URDF test, STL import, obj import

Demos3/bullet2/BasicDemo/MyDebugDrawer.h

@@ -60,7 +60,9 @@ public:
 
 	virtual void	drawContactPoint(const btVector3& PointOnB,const btVector3& normalOnB,btScalar distance,int lifeTime,const btVector3& color)
 	{
+        drawLine(PointOnB,PointOnB+normalOnB,color);
 	}
+     
 
 	virtual void	reportErrorWarning(const char* warningString)
 	{