erp5_hr_calendar: we need possibility to define start dates on time tables

Calculation of periods needs a starting date to know how to repeat the period.

bt5/erp5_hr_calendar/PortalTypePropertySheetTemplateItem/property_sheet_list.xml

@@ -9,6 +9,7 @@
  </portal_type>
  <portal_type id="Time Table">
   <item>DublinCore</item>
+  <item>Task</item>
  </portal_type>
  <portal_type id="Time Table Line">
   <item>Amount</item>

bt5/erp5_hr_calendar/bt/template_portal_type_property_sheet_list

@@ -6,3 +6,4 @@ Time Table Line | Amount
 Time Table Line | SortIndex
 Time Table Line | TimeTableLine
 Time Table | DublinCore
+Time Table | Task
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