WORLDGUARD-3403 - Reported by RoyCurtis

AFAIK, the notify-enter and notify-leave flags are only useful for moderators; that is, everybody with the worldguard.notify permission will receive region entry/exit notifications, even if they are not an owner or member of that region.

It would be nice to have a way for region owners to be notified if somebody has entered/exited their region. Some ideas:

• Extend worldguard.notify to worldguard.region.notify.* with e.g.
  ** worldguard.region.notify.own.* for notifications to region owners on their own regions
  ** worldguard.region.notify.member.* for notifications to region members on their own regions
  ** worldguard.region.notify.* for current behavior
• Change notify-enter and notify-leave behavior to work per-region for owner instead of everyone with notify permissions
• Create new doorbell or alert-enter/alert-leave flags to work as above idea

A use case for this behavior, as desired by a player on my server, is to monitor when players enter or leave a shop so that the shop-keeper may attend to them. Thoughts?