The `duration` used by the dhtmlx gantt component corresponds to the calendar duration of the event divided by 3. This makes sense only for events spanning full days, and for working times with 8 hours per day. Unfortunately these hypotheses do not hold for most cases inside OpenERP, so we should hide this information. The actual duration of the items can always been viewed by clicking on the corresponding label. bzr revid: odo@openerp.com-20120702133016-gzscrpbbh1a9mgez