Deal with inactive users profile's

When a user is set to inactive XWiki should apply some specifics :

• User document is set to "hidden" in order for common Users not to be bothered with them any more. They won't see them in :
  • the User Directory
  • the Search Engine
  • globally any place but the full doc index and in links (like creator page links)
• Add a visual differentiation to his page
  • Add a ribbons over his profile picture
  • Add a note on top of the page to explicitly show that the user is inactive since the XX/XX/XXXX and that his information may be obsolete (See screenshot)

For admins :

• Have a dedicated User directory to see all inactive user OR see inactive user with a visual differentiation into it (like grey name)
• Have an option (on the profile page and on the inactive user directory) to re-activate the account
• Have an option to delete the account (may raise some other issues to be dealt under an other task)