added 2 new flag types: notify user and notify moderators

fixed up messed up user navigation
refactored

lib/guardian.rb

@@ -294,6 +294,7 @@ class Guardian
     # You can only undo your own actions
     return false unless @user
     return false unless post_action.user_id == @user.id
+    return false if post_action.is_private_message?
 
     # Make sure they want to delete it within the window
     return post_action.created_at > SiteSetting.post_undo_action_window_mins.minutes.ago