Admin notifications about new pending registrations

There is no way to know about new registrations waiting for admin approval without opening the ACP.

Currently, you can only set receive notifications about all registrations (including successful), which is not necessary.

Please, add this option, because my pending users sometimes have to wait few days until I open ACP and see them. Usually, I don't have a need to open ACP every day and, of course, I forget about the pending list.