Modif to perform in 9.0-rc releas 

add variable button in study : http://jira.obiba.org/jira/browse/MICA-1227
Add study title in variable page : http://jira.obiba.org/jira/browse/MICA-1228
Remove datashiel module : http://jira.obiba.org/jira/browse/MICA-1226