- [bug] the value of a composite attribute is now

- [bug] the value of a composite attribute is now
expired after an insert or update operation, instead
of regenerated in place.  This ensures that a
column value which is expired within a flush
will be loaded first, before the composite
is regenerated using that value.  [ticket:2309]

- [bug] The fix in [ticket:2309] also emits the
"refresh" event when the composite value is
loaded on access, even if all column
values were already present, as is appropriate.
This fixes the "mutable" extension which relies
upon the "load" event to ensure the _parents
dictionary is up to date, fixes [ticket:2308].
Thanks to Scott Torborg for the test case here.