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/Bullet2RigidBodyDemo.cpp

@@ -167,6 +167,7 @@ Bullet2RigidBodyDemo::Bullet2RigidBodyDemo(SimpleOpenGL3App* app, CommonPhysicsS
 void Bullet2RigidBodyDemo::initPhysics()
 {
 	MyGraphicsPhysicsBridge glBridge(m_glApp);
+	glBridge.setUpAxis(1);
 	m_physicsSetup->initPhysics(glBridge);
 	m_glApp->m_instancingRenderer->writeTransforms();