Map "shared" group to "locals" during ibay migration. Refs #2492
Change default ibay owner from root to admin. Refs #2573
SharedFolder UI module: "Authenticated users" label renamed "Local users". Refs #2492

The "authenticated" term can be misleading with Samba ADS role, for instance.
Migration: replace "shared" group with "locals" when restoring Posix ACLs. Refs #2492