Use uwsgi instead of default werkzeug
Since version 4.6, we can easily run trytond as a WSGI application.
The werkzeug documentation [1] does not recommend to run their server in production. So I think we should lead by example and run the Docker image with a production ready server.
I propose to use uwsgi as it seems to be fast with a good set of options to tune it.
uwsgi should be just the default CMD, user may still want to run trytond (or trytond-cron) and it should serve the same way as trytond.
Also I think we should use the http-socket [2] to allow to connect to it directly for debugging and it keep the same behavior for existing deployment. User who wants to use wsgi protocol could still append a "--socket" argument.
I think we should implement this on both 4.6 and 4.8 images.
[1] http://werkzeug.pocoo.org/docs/0.14/serving/
[2] https://uwsgi-docs.readthedocs.io/en/latest/HTTP.html#http-sockets