Add admin UI to Restore/Confirm moderation of notifications

Add the admin UI needed to restore the hidden proposal notifications
when hidden by moderator. The admin can restore them or confirm
the moderation made by moderator, just like proposals.

config/locales/es/admin.yml

@@ -940,6 +940,15 @@ es:
           without_confirmed_hide: Pendientes
         title: Propuestas ocultas
         no_hidden_proposals: No hay propuestas ocultas.
+    proposal_notifications:
+      index:
+        filter: Filtro
+        filters:
+          all: Todas
+          with_confirmed_hide: Confirmadas
+          without_confirmed_hide: Pendientes
+        title: Notificaciones ocultas
+        no_hidden_proposals: No hay notificaciones ocultas.
     settings:
       flash:
         updated: Valor actualizado