more refactoring, removed PhysicsInterface, cleaned up demos to make use of btDynamicsWorld derived classes.

removed two cached optimizations, type in btTransform and cached inverse transform (todo: test performance impact)
committed fixes that make the code adhere to 'who creates it, also destroys it'

src/BulletCollision/CollisionDispatch/btCollisionObject.cpp

@@ -25,8 +25,7 @@ btCollisionObject::btCollisionObject()
 		m_ccdSweptShereRadius(0.f),
 		m_ccdSquareMotionTreshold(0.f)
 {
-	m_cachedInvertedWorldTransform.setIdentity();
-
+	
 }