Anonymous read-only UI

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While it is trivial to grant read-only rights to entire issues and one-off articles to role reader or even member if it is to be totally public, the UI to read those isn't user-friendly.

• Confirm that read-only rights could be granted to the anonymous user which isn't even logged in.

• When not logged in, a read-only navigation and display mechanism should be offered if there are any articles visible to the current user.

• When logged in, re-use the read-only navigation for role 'reader'.