OR-651 add /api/user/notifications/:uuid/acknowledged routes

Conflicts:
	backend/webserver/controllers/usernotification.js
	backend/webserver/routes.js
	doc/REST_user.md
	test/unit-backend/webserver/controllers/usernotification.js

Conflicts:
	doc/REST_user.md

Conflicts:
	backend/webserver/routes.js
Merge pull request #454 in OR/rse from ~SLEMAISTRE/rse:OR-652 to master

* commit 'f2b3ead2850fe608d77f782817e25d5386d3fd00':
  OR-651 add /api/user/notifications/:uuid/acknowledged routes
OR-652 fix linters