[Tails-l10n] [review](de) download page typos fixed

Hi,

I found a typo in the amnesia-news mailinglist submit button
("Abbonieren" instead of "Abonnieren") and changed two sentences. The
other changes are because poedit wrapped some lines for some reason.

Please review
https://gitorious.org/flapflap/tailsxlat.git
branch de-download

Commit
77d4b81 some typos fixed and lines wrapped

Cheers!
~flapflap