Order notifications by updated_at instead of created_at

closes #7568

Changelog.md

@@ -3,6 +3,7 @@
 ## Refactor
 * Remove title from profile photo upload button [#7551](https://github.com/diaspora/diaspora/pull/7551)
 * Remove Internet Explorer workarounds [#7557](https://github.com/diaspora/diaspora/pull/7557)
+* Sort notifications by last interaction [#7568](https://github.com/diaspora/diaspora/pull/7568)
 
 ## Bug fixes
 * Fix displaying polls with long answers [#7579](https://github.com/diaspora/diaspora/pull/7579)

app/controllers/notifications_controller.rb

@@ -32,7 +32,7 @@ class NotificationsController < ApplicationController
     @notifications = WillPaginate::Collection.create(page, per_page, Notification.where(conditions).count ) do |pager|
       result = Notification.where(conditions)
                            .includes(:target, :actors => :profile)
-                           .order('created_at desc')
+                           .order("updated_at desc")
                            .limit(pager.per_page)
                            .offset(pager.offset)