Add back button

app/templates/corpora/corpus_analysis.html.j2

@@ -1,7 +1,9 @@
 {% extends "full_width.html.j2" %}
 
 {% block page_content %}
+
 <div class="col s12 m3 l3 sticky">
+  <a class="waves-effect waves-light btn" href="{{ url_for('corpora.corpus', corpus_id=corpus_id) }}"><i class="material-icons left">arrow_back</i>Back to corpus overview</a>
   <div class="card">
     <form id="query_form" method="POST">
     <div class="card-content">