Update cookies page

Includes:
- new content
- added option to turn analytics on/off
- non-js version for the on/off switch
- a banner to confirm user's choice was saved,
  shown when they click the save button
- the cookie banner that appears on all other
  pages removed from this page

app/assets/stylesheets/main.scss

@@ -82,6 +82,7 @@ $path: '/static/images/';
 @import 'views/send';
 @import 'views/get_started';
 @import 'views/history';
+@import 'views/cookies';
 
 // TODO: break this up
 @import 'app';