Fix-committed: #11616

Note that this merge does *not* close #9707.

Refs: #9707

refs: https://mailman.boum.org/pipermail/tails-dev/2016-November/011034.html

This link and the system menu screenshot provided basically the same
information: clarifying the context, so let's stick to the image that
doesn't require people to go to a different page.

Reusing that same image also makes sense as it displays the two buttons
that we are referring to.

Merge remote-tracking branch 'spriver/web/11385-update-shutdown-to-jessie' into web/11385-update-shutdown-to-jessie

Since we're breaking PO strings anyway, let's clean up a bit.

Merge remote-tracking branch 'spriver/feature/11243-OpenPGP-Applet-screenshots' into feature/11243-OpenPGP-Applet-screenshots