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/views/cookies.scss

@@ -0,0 +1,17 @@
+.cookie-settings__form-wrapper {
+  display: none;
+
+  .js-enabled & {
+    display: block;
+  }
+}
+
+.cookie-settings__no-js {
+  .js-enabled & {
+    display: none;
+  }
+}
+
+.cookie-settings__confirmation {
+  display: none;
+}