Installation page layout.
page-avec-nav.mako create.
page-avec-nav and site layout.
Add documention for API controllers.
installation.mako layout
Merge branch 'master' of github.com:stanislasrybak/openfisca-web-site into stanislasrybak-master

Conflicts:
	openfisca_web_site/templates/tree/installation.mako