Personalization of Codalab front page with logos of servers hosting organizations

[acletournel]

To better publicize the hosting servers organization of an instance, their logos are added on the front page:

• White version of the logos will be inserted aligned right, in the top banner of Codalab:

• The url of each institution is linked to the logos:

www.lisn.upsaclay.fr
www.universite-paris-saclay.fr
www.cnrs.fr

• Documentation of the feature in the wiki should allow any Codalab instance admin to personalize his front page with his own logos/urls, as a new production server setting step : https://github.com/codalab/codalab-competitions/wiki/Production-Server-Settings

[Didayolo]

Done on Codabench