Investigate Jenkins Job DSL

We need to stop using freestyle jenkins jobs. Newly created jobs should use Job DSL.
We need to investigate how to use it.

• check examples http://post-office.corp.redhat.com/archives/ci-infra-list/2019-February/msg00069.html
• create one simple job in our jenkins
• document usage and inform all team members

We don't want to update our existing jobs at this stage. This will be done later in stage 2.