Here's we're upgrading so saying (1) for the other Tails and (2) for the
original and important one feels weird. Even more so on the
upgrade-tails scenario where we don't have these numbers already.

This scenario will run Tails Installer *three* times but we can't pass
different contexts to the inline of install_final.inline, so let's
duplicate and simplify these instructions twice at the beginning to
create the temporary Tails.

We provide more precise instructions and troubleshooting when restart
for the first time, independently of whether it's a temporary Tails (for
Windows, Linux, and Mac) or a final Tails (for Debian).

- Add usual CSS tricks to expert.css
- Don't display steps and states for expert.
  This make the layout of command line instructions much easier, and
  experts don't need them anyway :)
- Prepare the work for the Debian scenario.

For the first testing sessions it won't be in Debian backports.

This scenario will be advertised as "using the command line and GnuPG"
which should filter out people quite a bit. So people actually opening
this page could be interested in learning how to do this.