Simplify permission assignments

• On first access, if Tuleap says anon can read, allow them
• If not ask for login
• After login, if user can read allow them, if not, block them
• After login, assign additional groups for writers and admins if allowed

Change-Id: I1a15c370abae5f322e5d4a882d52e03abc699458
(cherry picked from commit ab56d6953e1476cf8c46612bf2ed487adab44708)