UX : New group for newsletters in left content tree #25
Description
It could be clearer and avoid confusion for OWnewsletter users to have 2 distinct groups in left content tree :
1 - Mailing lists with title "Les listes de diffusions"
2 - Newsletters with title "Les newsletters"
The root node "newsletter_system" and "Systèmes de newsletter" title are not necessary in the content tree and should be masked.