command to remove old AERs (bug 980336)

Some apps still had IARC-related game region exclusions via AddonExcludedRegion objects. This command removes old AERs on the heuristic that AERs are old if the app is a game that only has Germany+Brazil excluded.

It doesn't cover 100% of the cases. Only apps that have untouched regions where the system only disabled Brazil+Germany because they were unrated games. Apps that have been manually excluded from other regions will have to manually re-include Brazil+Germany.

@robhudson