DirectoryHelper bound to (x)vocabulary schemas

DirectoryHelper is a helper class used for several components which use directories as data source. It is sadly tightly bound to the vocabulary or xvocabulary schemas. It expects the presence of the fields 'id', 'label', 'ordering' even if the vocabulary uses a different schema or simply uses a different idField.

This fact makes it impossible to use those components with directories that don't strictly adhere to the vocabulary schema.

This bug was mentioned in the forum post at: http://forum.nuxeo.com/t/4008/ but I did not find it elsewhere.