Private space UI update

[valentinRyckaert]

Summary of changes

• adding information on a space page and on the index page for spaces to see privacy-related information.

Motivation and context

A user can't check if a space he can see is private or not, who are the administrators and which group is necessary to access it. The only way is to have access to the edition form.

Checklist

• I have read and followed the CONTRIBUTING guide.
• I confirm that I have the authority necessary to make this contribution on behalf of its copyright owner and agree to license it to the TeSS codebase under the BSD license.