refine pipeline setup

I refactored the pipeline setup.

First of all we now use our own ci-image which speeds up builds as we don't have to install all software again

Then I merged all the pipeline files into one big file as we can then run jobs in parallel. Ansible can easily install dependencies while terraform is planing and applying the infrastructure, but we can still specify dependencies between jobs to avoid running into errors.

Somehow kubespray doesn't find any hosts... I'll now work on terraform generating an inventory file as output.