wait-for-it.sh hardcoded to mongo:27017

[mueller-ma]

I'd like to run mongodb on a different hostname and port than the default mongo:27017, but that's hardcoded in the Dockerfile: https://github.com/colloqi/pisignage-server/blob/master/Dockerfile#L20

Could you make this configurable by enviroment variables that can be set in docker-compose.yml?