erp5_interface_post : add InterfacePost property sheet on Post portal types

bt5/erp5_interface_post/PortalTypePropertySheetTemplateItem/property_sheet_list.xml

+<property_sheet_list>
+ <portal_type id="Internet Message Post">
+  <item>InterfacePost</item>
+ </portal_type>
+ <portal_type id="Letter Post">
+  <item>InterfacePost</item>
+ </portal_type>
+</property_sheet_list>
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bt5/erp5_interface_post/bt/template_portal_type_property_sheet_list

+Internet Message Post | InterfacePost
+Letter Post | InterfacePost
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