Account deletion (#3728)

* Add form for account deletion

* If avatar or header are gone from source, remove them

* Add option to have SuspendAccountService remove user record, add tests

* Exclude suspended accounts from search

config/routes.rb

@@ -66,6 +66,7 @@ Rails.application.routes.draw do
     end
 
     resource :follower_domains, only: [:show, :update]
+    resource :delete, only: [:show, :destroy]
   end
 
   resources :media, only: [:show]