Instead of `Pleroma.User.all_superusers()` we now use `Pleroma.User.all_superusers(:report_handle)`
I also changed it for sending emails, but there were no tests.
* These are the first small steps for issue 2034 "Reports should send a notification to admins".
* I added a new type of notification "pleroma:report" to the the database manually (a migration will need to be written later)
* I added the new type to the notification_controller
* I made the view return the notification. It doesn't include the report itself (yet)
Ilja