Add csv download link to group details page

templates/jwinf/group.hbs

@@ -29,7 +29,8 @@
 <div class="columns">
    <div class="column is-8 is-offset-2">
       <h4 class="subtitle is-5">Mitglieder</h4>
-      {{#if member}}      
+      {{#if member}}
+         Mitgliederdaten herunterladen: <a href="download/{{group.id}}">{{group.name}}.csv</a>
 <table class="table">
    <tr>
       <th>Name</th>