Bug 1009883 - Implement Nightly First Run page redesign

This will never be exposed, it's actually only a placeholder for localizers to get inspired. Locales will provide content for the whole {% l10n promo_locale %} block. For instance: http://viewvc.svn.mozilla.org/vc/projects/mozilla.com/trunk/locales/fr/templates/firefox/nightly_firstrun.html?view=co&content-type=text%2Fplain