WIP: Upload issues

This PR collects all commits related to upload issues #30 (closed), #18 (closed), and others

app/templates/files.html

 {%  extends 'base.html' %}
 {%  block body %}
 <div>
+    <p>
+        <form action="{{ back_link }}" method="get" id="back_form"></form>
+        <button type="submit" form="back_form">Back to results</button>
+    </p>
     {% if link_to_parent %}
         <p>
             <a href="/files{{ req_path }}/..">Back to parent directory</a>