`pileItemOrder` is too complicated and it's name suggest to be a item property

[flekschas]

Since we call many item-specific properties pileItem, I would assume pileItemOrder accepts a callback function that look like (itemState, itemId, itemIndex) => {} but this is not the case. It's not a pile specific callback.

I suggest renaming it to pileOrderItems and to make it a pile property, i.e., it should get pileState as it's argument and return an order array of itemIDs. The item id to item object mapping can be done by the user.