S allius/issue394 (#400)

* store logging path in Config class

* rename template files and page files

* jump to referer page

- after changing the language, we jump to
  the referer page, if the attribute exists

* build and send list of log-files

* rename Download page into Log files

* initialize log-path in test config

* improve dashboard unit tests

 - add log file tests
 - check content-languages after language switch

* initialize config structure for log-file tests

* add test log file to project

* add sub_dir to test log path

- non files must be skipped. To test this we add
  a sub directory to the test log directory

* add german translations

* set quart debug flag for debug versions

* update changelog

app/src/web/templates/page_logging.html.j2

@@ -0,0 +1,11 @@
+{% extends 'base.html.j2' %}
+
+{% block title %} TSUN Proxy - Downloads {% endblock title%}
+{% block menu3_class %}w3-blue{% endblock %}
+{% block headline %}<i class="fa fa-file-export fa-fw"></i>  {{_('Log Files')}}{% endblock headline %}
+{% block content %}
+  <div class="w3-container" id="file-list"></div>
+{% endblock content%}
+
+{% block footer %}{% endblock footer %}
+