recomputeSingleDocumentChangeSet does not work for collections

If you have a document with a collection, during computation of the changeSet before persist a reference to that collection is placed in originalData, not a copy. Therefore, if you change the collection in an onFlush event listener, then call recomputeSingleDocumentChangeSet, the changes to the collection are not recognised, because the originalData has changed also.

I will create a test, and hopefully fix for this soon.