add stylesheet fot QTreeView objects
add stylesheet fot QTreeView objects

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