Better error handling in CorpusAnalysisApp

app/templates/corpora/analysis.html.j2

@@ -48,8 +48,9 @@
 {{ super() }}
 <div class="modal no-autoinit" id="corpus-analysis-app-init-modal">
   <div class="modal-content">
-    <h4>Initializing session</h4>
+    <h4>We are preparing your analysis session</h4>
     <p>
+      Our server works as hard as it can to prepare your analysis session. Please be patient and give it some time.<br>
       If initialization takes longer than usual or an error occurs, <a onclick="window.location.reload()" href="#">reload the page</a>.
     </p>
     <div class="progress">