erp5_production_planning: default title is "Production Plainng at date"

bt5/erp5_production_planning/SkinTemplateItem/portal_skins/erp5_production_planning/ProductionPlanning_init.py

@@ -15,4 +15,5 @@ else:
 context.edit(
   start_date=start_date,
   stop_date=stop_date,
+  title = context.Base_translateString('Production Planning at ${date}', mapping= {'date': start_date.Date()}),
   production_planning_period = context.portal_preferences.getPreferredProductionPlanningPeriod())