Provide Repository Implementation for Directory

The goal is to provide an implementation of the Directoryfactory that uses Nuxeo Core as Storage.

Since directory Entries are Documents, this should not be too complicated.

Expected gains include :

• ability to define an ACL for each directory (via XML descriptor)
  • define who can Read/Write entries
• ability to activate auto-versioning on the entries

This is part of the nuxeo-directory-addons addon.