First commit of the i18n feature.

Most of the strings were exported in lang/en-GB.php.
i18n - lang en-GB and fr-FR

eLabFTW is now localized ! Next languages will probably be : spanish and
brazilian.
Bootstrap.

Add bootstrap via bower.
s/status/statut in FR.
change css of alerts (wip)
put columns on search
register page is now with grid layout
ucp is now bootstraped
bring back the good colors for alert messages
editXP is now bootstrapped
put images 5px up so they are aligned

and some other bugfixes