cubicweb #1402 A more friendly 404 [open]

Based on :

http://googlewebmastercentral.blogspot.com/2008/08/make-your-404-pages-more-useful.html

or http://www.alistapart.com/articles/amoreuseful404

Make the "this resource does not exist" on a wrong URL more user friendly - and also the "No result matching query" (when search returns no results) more friendly.

prioritynormal
typeenhancement
done in<not specified>
load0.500
load left0.500
closed by<not specified>