Now we ask the dev to create the "ofn" user as precondition. This is
way easier than developing a script that fits all possible setups.
It also stops requiring a particlar Postgres version. Although in
production we use 9.5 it is very unlikely we will use any
version-specific feature in the near future. This should make it a bit
easier for new devs to set up their environment.
It aims to aid new open source contributors on setting up their dev
env by means of a single command with meaningful output.
Although ofn-install ansible scripts also work for development we don't
want to add too much burden to those single-time beginner contributions.