svn 778406: OrderItem audit-log

[Adam Heath <do...@brainfood.com>]

(sorry, I've already deleted the mail from 05-25 that mentioned this
commit).

This change enabled entity-audit-log on a few fields in the order
system, so that history can be tracked.  It then provides screens to
see these changes.  This is a cool feature, but unfortunately, it was
done the wrong way.

It implements business logic by making use of the entity audit system.

This is bad, because there is no way to disable it, *at all*.  You'd
want to disable it when writing an importer from a legacy system,
where you need to maintain the date filter/timestamp fields exactly as
they are in the old system.  If this was done as an eca, then at least
using default-no-eca delegator would work.  Additionally, because of
how this is done, the timestamp encoded in the audit log for the
change is *now*, not the point in history where it actually took place.

There is no way to make this per-ProductStore(not a really big deal),
nor any other kind of constraint.