Miscellaneous documentation updates
Setting in place some sections to be filled out, and starting a new overview section.
[A venir] Mise en place de quotas sur nos instances GitLab. Plus d'information sur : https://doc-si.inria.fr/pages/viewpage.action?pageId=129728565
[Coming soon] Quotas installation on our GitLab instances. More information: https://doc-si.inria.fr/pages/viewpage.action?pageId=129728565
Setting in place some sections to be filled out, and starting a new overview section.