Id aliases interfere with item position when reconstructing revisions from the journal

[WardCunningham]

We have seen added items appear out of order when they are the same item copied to a page many times. The second and subsequent drops cause new non-duplicate ids to be created and the old id stored as an alias while the item is in the page. (The original id can be restored when copied to a non-conflicting page.)

The proper insertion point is identified by an after field. When this is absent or not found, the item is inserted at the beginning.