[frontend/plugins/scoreboard] edit config via frontend

[anthonygego]

Describe the bug
Since the merge of tasksets feature, courses data are in database and are not directly exposed to the course administrator via a YAML file.

The scoreboard plugin relies on the manual edition of the course structure dictionary. Therefore, it is not posible anymore to edit it without issuing a request in the database.

INGInious installation details

• Version: v0.9+

Expected behavior
We should have a specific page to edit these fields in the frontend.