add piwik installation

www/analytics/plugins/Installation/templates/welcome.twig

@@ -0,0 +1,45 @@
+{% extends '@Installation/layout.twig' %}
+
+{% block content %}
+<h2>{{ 'Installation_Welcome'|translate }}</h2>
+
+{% if newInstall %}
+    {{ 'Installation_WelcomeHelp'|translate(totalNumberOfSteps)|raw }}
+{% else %}
+    <p>{{ 'Installation_ConfigurationHelp'|translate }}</p>
+    <br/>
+    <div class="error">
+        {{ errorMessage }}
+    </div>
+{% endif %}
+
+<script type="text/javascript">
+    <!--
+    $(function () {
+        // client-side test for https to handle the case where the server is behind a reverse proxy
+        if (document.location.protocol === 'https:') {
+            $('p.nextStep a').attr('href', $('p.nextStep a').attr('href') + '&clientProtocol=https');
+        }
+
+        // client-side test for broken tracker (e.g., mod_security rule)
+        $('p.nextStep').hide();
+        $.ajax({
+            url: 'piwik.php',
+            data: 'url=http://example.com',
+            complete: function () {
+                $('p.nextStep').show();
+            },
+            error: function (req) {
+                $('p.nextStep a').attr('href', $('p.nextStep a').attr('href') + '&trackerStatus=' + req.status);
+            }
+        });
+    });
+    //-->
+</script>
+
+{% if not showNextStep %}
+    <p class="nextStep">
+        <a href="{{url}}">{{ 'General_RefreshPage'|translate }} &raquo;</a>
+    </p>
+{% endif %}
+{% endblock %}