Remove single alias/implication requests.

* Remove the single alias and implication request forms. From now
  on, bulk update requests are the only way to request aliases or
  implications.

* Remove the forum topic ID field from the bulk update request form.
  Instead, to attach a BUR to an existing topic you go to the topic then
  you click "Request alias/implication" at the top of the page.

* Update the bulk update request form to give better examples for the
  script format and to explain the difference between aliases and
  implications.

config/routes.rb

@@ -267,13 +267,11 @@ Rails.application.routes.draw do
       post :approve
     end
   end
-  resource :tag_alias_request, :only => [:new, :create]
   resources :tag_implications do
     member do
       post :approve
     end
   end
-  resource :tag_implication_request, :only => [:new, :create]
   resources :uploads do
     collection do
       post :preprocess