Titles for help links and default for not logged in users

[Jeremy Hopkins]

1. add titles / heading to "header navigatoin" admin settings to make it clearer
2. add third help link which is the one to show to non logged in users

Thus we can have password reset help for thost that cannot login, along with the current staff / student links.

[Jeremy Hopkins]

Navbar no longer shows at all for logged out users so this change would no longer work.