Remove from the views elements which users can't really interact with

[Caio Begotti]

Today we display navbar links for projects, dependencies and jenkins servers to anyone, right in the login view, without it being necessary. We should shrink the navbar to the minimum until the user is authenticated, specially because they will be dumbly redirected if they try to access those links anyway.

Also, we should remove the jenkins entry from the navbar for all users except for Django's superusers because no one can (or should) manage the jenkins servers. Regular users should not see that, not even staff users should be able to see it IMHO.

Finally, we should not display create, edit and delete buttons after table lists with projects and dependencies if the user has no access to use those. In theory only staff and superusers should see those buttons. Regular users can only interact with builds (including the build buttons to trigger a new run, of course).

[Daniel Manrique (roadmr)]

I think this is pretty clear, so it's just about making views check permissions and act accordingly. Testing is going to be the most fun part of this :)