dmails: allow Members to mark dmails as spam.

* Allow Members to mark dmails as spam or not spam (previously Gold only).
* Replace spam and ham endpoints with single update endpoint.

config/routes.rb

@@ -110,11 +110,7 @@ Rails.application.routes.draw do
       put :cancel
     end
   end
-  resources :dmails, :only => [:new, :create, :index, :show, :destroy] do
-    member do
-      post :spam
-      post :ham
-    end
+  resources :dmails, :only => [:new, :create, :update, :index, :show, :destroy] do
     collection do
       post :mark_all_as_read
     end