Add moderator role and add pundit policies for admin actions (#5635)

* Add moderator role and add pundit policies for admin actions

* Add rake task for turning user into mod and revoking it again

* Fix handling of unauthorized exception

* Deliver new report e-mails to staff, not just admins

* Add promote/demote to admin UI, hide some actions conditionally

* Fix unused i18n

config/routes.rb

@@ -137,6 +137,13 @@ Rails.application.routes.draw do
       resource :suspension, only: [:create, :destroy]
       resource :confirmation, only: [:create]
       resources :statuses, only: [:index, :create, :update, :destroy]
+
+      resource :role do
+        member do
+          post :promote
+          post :demote
+        end
+      end
     end
 
     resources :users, only: [] do