use plone.dexterity.interfaces.IEditFinishedEvent instead of IObjectModified
to avoid massive performance lag
in the tests, we also need to notify the new event (IEditFinishedEvent)
Add an upgrade step that removes the old handler registration and enables the new
handler registration
update changelog
better description
Merge pull request #7 from plone/use_editfinishedevent

Use IEditFinishedEvent instead for IObjectModifiedEvent for triggering language-independent handling