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

gulpfile.js

@@ -146,6 +146,7 @@ const javascripts = () => {
     paths.src + 'javascripts/analytics/analytics.js',
     paths.src + 'javascripts/analytics/init.js',
     paths.src + 'javascripts/cookieMessage.js',
+    paths.src + 'javascripts/cookieSettings.js',
     paths.src + 'javascripts/stick-to-window-when-scrolling.js',
     paths.src + 'javascripts/apiKey.js',
     paths.src + 'javascripts/autofocus.js',