With previous configuration format rules were not ordered between groups and
thus not predictable. Also in some cases `any` must have been a higher
precedence than `groups`. Flattening the rules let the user apply whatever
policy he can think of.
When several rules match the (subject, domain, resource), the first one is
applied.
NOTE: This commit changed the format for declaring ACLs. Be sure to update
your configuration file before upgrading.
Clement Michaud