[Tails-dev] Please review and merge doc/administration_passw…

Hi,

Some users are confused by the fact that the administration password is
the password of a user with full sudo rights, and not a plain root password.

I think that in practice, this distinction mostly make sense when trying
to open a root terminal. So I tried to fix that by adding a note on how
to open a root terminal.

I thought that was better than digging into a more abstract explanation
about the difference between "root" and "user with sudo rights", since
that might have confused other users.

That's commit 03e72ff of branch doc/administration_password.

Since I was already modifying this page, I also change a phrasing to be
more precise in c404f44.

Please review and merge.

That's a follow up on whisperback bug c2e683af9a0eff2f53661826c36f999a
(24/11/2012).