Retired artifacts

• Do not search among or display retired artifacts
• List all retired artifacts in an index accessible to admins on the admin site /admin/artifacts/retired
• Let a user with sufficient access retire or "un'-retire an artifact
• in edit artifact form, add a retired section so we can modify the data for the associate retired_artifacts entry (create entry when artifact gets retired)
• when someone links to the artifact no or /Pxxxxxx of a retired artifact, user should be redirected to the new entry with a flash message yellow / warning indicating this redirection happened and why. (only when the retired artifact is public)