Move requirements for Debian and Ubuntu version to the beginning of the scenario (#11017)
It's not nice to tell people they cannot finish a scenario after they started it. We could even move this information in the /install/os but this would: - Require more design and implementation. - Might be harder to make as visible and information without polluting this page for everybody else. Anyway, in a couple of months, Debian Wheezy will be unsupported officially and Trusty will be superseded by a new LTS so we don't need a super fancy long-term solution.