XWiki FusionDirectory integration

Goal: define roles and permissions in FusionDirectory, and enforce these policies in XWiki. Example: a Project Manager can administrate the wiki of his project, the contributors to the project can edit the wiki, the visitors can only view the wiki.

Some remarks:

• the other CMS that integrate with FusionDirectory such as WordPress, DokuWiki Piwik) repliate LDAP groups/roles in their internal database
• the existing LDAP XWiki mapping will allow to manage rights coming from the LDAP though. However we'll have to propagate the LDAP policies to each wiki. We could consider writing scripts for automating the process.
• the option not to replicate remains meaningful according to OpenSides (FusionDirectory editor) but it is probably much more complex to implement.