Display navbar to logged out users

[Jeremy Hopkins]

It used to be possible to show the navbar so that Help and Tools links were available.

That needs to be put back recognising that none of the other links (calendar, my courses etc) should show for a non logged in user.

This needs to be added as an option in admin so we can choose whether to show the navbar or not to logged out users.

[Manoj Solanki]

Fix #870

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