Fix template FileField reading

This merge request fixes all templates where a FileField content was read directly rather than using the associated property who would give the correct output.

Fixes #566 (closed)

beat/web/dataformats/templates/dataformats/panels/editor.html

@@ -43,7 +43,7 @@
         </div>
       </div>
       {% endif %}
-      <textarea class="form-control" id="declaration-display">{{ object.declaration_file.read }}</textarea>
+      <textarea class="form-control" id="declaration-display">{{ object.declaration }}</textarea>
       <p class="help-block">{{ texts.json|safe }}</p>
     </div>
   </div>