Move piwik code into its own js file for compatability with CSP

public/assets/js/piwik.js

@@ -0,0 +1,13 @@
+// Piwik in its own js file to allow usage with a CSP policy
+
+var _paq = _paq || [];
+// tracker methods like "setCustomDimension" should be called before "trackPageView"
+_paq.push(['trackPageView']);
+_paq.push(['enableLinkTracking']);
+(function() {
+    var u="https://analytics.jmb.lv/";
+    _paq.push(['setTrackerUrl', u+'piwik.php']);
+    _paq.push(['setSiteId', '1']);
+    var d=document, g=d.createElement('script'), s=d.getElementsByTagName('script')[0];
+    g.type='text/javascript'; g.async=true; g.defer=true; g.src=u+'piwik.js'; s.parentNode.insertBefore(g,s);
+})();