add simple Dockerfile and docker-compose file

[Totto16]

This adds a Dockerfile and docker-compose.yml file, the README describes how to use them

fix two flask errors:

#  * Ignoring a call to 'app.run()' that would block the current 'flask' CLI command.
#    Only call 'app.run()' in an 'if __name__ == "__main__"' guard.

fix it, by checking, if the file is called directly or by imported by flask

WARNING: This is a development server. Do not use it in a production deployment. Use a production WSGI server instead. so I use the suggested package by flask itself

[mgerhold]

I don't think we need docker containers at this point, but thanks for your efforts, this might come in handy at a later point in time.