Remove postgres from Dockerfile

The concept of docker is all about micro services. Running
multiple services is a bad idea
Run trytond alone as microservice

* Removed sshd
  See why: http://blog.docker.com/2014/06/why-you-dont-need-to-run-sshd-in-docker/

* Removed supervisor since only trytond will now run
Change database to sqlite

It is the problem of downstream Dockerfiles to configure DB settings
Make server verbose