We want to provide a custom addLibrary factory for the
Library object, to be able to control the id of it.
Apparently this triggers a bug in CMFCore/TypesTool and
CMFPlone/Portal where the invokeFactory does not return the
id of the newly created object as it should.

When this has been fixed in Plone we can enable it again,
for now we rely on the *convention* of using 'videolibrary'
for the id.