- Session.refresh() now does an equivalent expire()

- Session.refresh() now does an equivalent expire()
on the given instance first, so that the "refresh-expire"
cascade is propagated.   Previously, refresh() was
not affected in any way by the presence of "refresh-expire"
cascade.   This is a change in behavior versus that
of 0.6beta2, where the "lockmode" flag passed to refresh()
would cause a version check to occur.  Since the instance
is first expired, refresh() always upgrades the object
to the most recent version.

- The 'refresh-expire' cascade, when reaching a pending object,
will expunge the object if the cascade also includes
"delete-orphan", or will simply detach it otherwise.
[ticket:1754]