add tooltips to the homepage buttons
add tooltips to the homepage buttons

rdebroiz/medInria-public,NicolasSchnitzler/medInria-public,aabadie/medInria-public,rdebroiz/medInria-public,rdebroiz/medInria-public,aabadie/medInria-public,aabadie/medInria-public,NicolasSchnitzler/medInria-public,NicolasSchnitzler/medInria-public