add Obj and STL import demo, work on URDF import

Demos/CommonPhysicsSetup.h

@@ -33,6 +33,8 @@ struct GraphicsPhysicsBridge
 		return 0;
 	}
 	
+	virtual void setUpAxis(int axis)=0;
+	
 };
 
 struct CommonPhysicsSetup

Demos/ConstraintDemo/ConstraintPhysicsSetup.cpp

@@ -22,6 +22,8 @@ void ConstraintPhysicsSetup::stepSimulation(float deltaTime)
 
 void ConstraintPhysicsSetup::initPhysics(GraphicsPhysicsBridge& gfxBridge)
 {
+	gfxBridge.setUpAxis(1);
+	
 	createEmptyDynamicsWorld();
 
 	gfxBridge.createPhysicsDebugDrawer(m_dynamicsWorld);