[WIP] partial port to bootstrap

Currently breaks everything (main page).
Partial port of header to bootstrap. Improvement of display on little screens.
Help required.
The pages which have been ported to bootstrap 2 already have a different header than the blueprint pages, so this PR is not needed for getting ride of blueprint. I guess we should port the header directly to bootstrap 3 has you said, so merge this in 0.6 with the whole port to bootstrap 3. I'm even wondering why do we need to specially port it to bootstrap if it looks nice without blueprint already. I mean, a framework is here to help you, not to add work to do...