replace Google analytics code with consent code

Author: smth

_includes/head.html

@@ -6,7 +6,15 @@
     <meta name="viewport" content="width=device-width, initial-scale=1">
 
     <link rel="apple-touch-icon" href="apple-touch-icon.png">
-    <link href="//fonts.googleapis.com/css?family=Cabin:400,400i,600,700" rel="stylesheet"> 
+    <link href="//fonts.googleapis.com/css?family=Cabin:400,400i,600,700" rel="stylesheet">
     <link rel="stylesheet" href="{{ "/css/main.css" | prepend: site.baseurl }}">
     <script src="{{ "/js/vendor/modernizr-2.8.3.min.js" | prepend: site.baseurl }}"></script>
+    {% if site.googleanalytics %}
+    <script>
+      var okiConsent = {
+        analyticsTrackingID: '{{ site.googleanalytics }}',
+      }
+    </script>
+    <script src="https://a.okfn.org/html/oki/consent/assets/js/consent.js"></script>
+    {% endif %}
 </head>

_layouts/default.html

@@ -56,16 +56,5 @@
           });
         </script>
         {% endif %}
-
-        {% if site.googleanalytics %}
-        <script>
-            (function(b,o,i,l,e,r){b.GoogleAnalyticsObject=l;b[l]||(b[l]=
-            function(){(b[l].q=b[l].q||[]).push(arguments)});b[l].l=+new Date;
-            e=o.createElement(i);r=o.getElementsByTagName(i)[0];
-            e.src='https://www.google-analytics.com/analytics.js';
-            r.parentNode.insertBefore(e,r)}(window,document,'script','ga'));
-            ga('create','{{ site.googleanalytics }}','auto');ga('send','pageview');
-        </script>
-        {% endif %}
     </body>
 </html>