hi there!

as our zope2 zodb grows we experience more and more conflicts
with long running transactions. so i'm going to rewrite these
methods to commit transactions in batches - here my attempt
to tackle this problem. the idea is to get a list of objects
to be modified in this transaction, break it down to batches
and commit after each batch was processed. to avoid zope's
retry-on-conflict machinery and still have a chance to retry
per batch transaction commits, the iteration over one batch
is guarded by a try:except ConflictError: and a retry logic.