Fill in create, edit, update, and destroy for keyword mutes interface.

Also add a destroy-all action, which can be useful if you're flushing an
old list entirely to start a new one.

config/routes.rb

@@ -66,7 +66,13 @@ Rails.application.routes.draw do
 
   namespace :settings do
     resource :profile, only: [:show, :update]
-    resources :keyword_mutes
+
+    resources :keyword_mutes do
+      collection do
+        delete :destroy_all
+      end
+    end
+
     resource :preferences, only: [:show, :update]
     resource :notifications, only: [:show, :update]
     resource :import, only: [:show, :create]