Convert membranes to a binary wrap rather than a wrap stack.
Currently, wrapped nodes store a stack of the membranes they are wrapped with, and are only unwrapped if they pass the opposite direction through the "top" membrane they are wrapped with. This leads to complexity and confusion when multiple wraps are added to an object.
Instead, we should just track which membranes an object is wrapped with irrespective of the order or count of those wraps. Wraps will only be added when the object has not yet been wrapped by that membrane.