Bug#637453: lower priority of root's password, use sudo in standard install

[Christian PERRIER <bubulle@debian.org>]

+1 on both remarks by Colin (not agreeing with sudo by default....and
the fact that the remark about Ubuntu wasn't appropriate).

Still, Miguel, thanks for raising these questions again. Sometimes,
conditions change and, at least, re-asking ourselves whether choices
made some years ago are still valid is a good idea.

Here, however, I think we shouldn't change anything (except the root
password confirmation as mentioned by Colin).