Always use an external uWSGI server to run the web service.

Added `waitress` dependency. For performance and security reasons, it's
better to always run the Flask application inside of a uWSGI server.

`waitress` also makes things easier by avoiding to ask the user to
manually provide the external executable arguments, as it was the case
with `uwsgi` and `gunicorn`.

docs/source/conf.py

@@ -301,6 +301,7 @@ autodoc_mock_imports = [
     'bleak',
     'bluetooth_numbers',
     'TheengsDecoder',
+    'waitress',
 ]
 
 sys.path.insert(0, os.path.abspath('../..'))