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/i18n.py

@@ -38,5 +38,8 @@ def utility_processor():
 async def set_language(language=None):
     if language in LANGUAGES:
         session['language'] = language
-        return redirect('../#')
+
+        rsp = redirect(request.referrer if request.referrer else '../#')
+        rsp.content_language = language
+        return rsp
     return abort(404)