notifications post group
Categories: added get_categories_from_node_id

@ludov04: you can use: `get_all_root_categories()` and `get_categories_from_node_id(X, false)`
notif content
merge
fixing bug
improve group
gestion de la suppression d'un groupe dans les notifs
update group
- refresh when add
- no more join on group page if member
pif Merge branch 'master' of github.com:matttbe/SIT

Conflicts:
	website/Solidare-IT-g6/db/schema.rb
merge