tasks #7338: Add unsuscribe button on each artifact

This task is part of story #2501 : be able to unsuscribe to an artifact

- add button to unsubscribe within each artifact
- if user, click on it, he will no longer receive a notificatio
- if he reactivat ethe notification, he will receive againthe notification

Change-Id: I6799edbea470153b9faa9188b709cb85d532445e
Merge commit 'refs/changes/98/2898/8' of ssh://gerrit.tuleap.net:29418/tuleap into stable

* ssh://gerrit.tuleap.net:29418/tuleap:
  tasks #7338: Add unsuscribe button on each artifact
This is Tuleap 7.3.99.68

Change-Id: I2bcba62b1fb71aff90f655ef8c814eda6a76e6ca