access_level: Removing allowed_users from Article's setings_itens and seting it as has_and_belongs_to_many with Person
(ActionItem2852)

Signed-off-by: Athos Ribeiro <athoscribeiro@gmail.com>
Signed-off-by: Fabio Teixeira <fabio1079@gmail.com>
Signed-off-by: Tales Martins <tales.martins@gmail.com>