Broken "blueprints" links in local documentation

Following “blueprints” link in local doc leads to an empty page (`wiki/src/blueprint/faq.mdwn`)

We could use a [[!tails_blueprint ]] thing that always point to the online version, just like we did for todo before migrating to Redmine.

When using the help browser, Internet link opens in Iceweasel, so that proposal should solve the issue.

Original created by @alant on 6586 (Redmine)

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