AdministrationService.getPresentationLocales() should return results with a correct and consistent order

In AdministrationServiceImpl.getPresentationLocales() the set we return is a HashSet, but this causes us to lose the ordering of locales (that ultimately comes from an admin-configured global property)

Instead we should use a LinkedHashSet, in order to preserve the order of locales we get from getAllowedLocales() (and ultimately the admin configured via a global property).