Concourse CI pipeline for stable/1.7.x

[sevein]

This pull request brings a new Concourse CI pipeline for AM17.

Links:

• Web interface
  https://ci.archivematica.org
• Browse the ci directory
  https://github.com/artefactual-labs/am/tree/dev/pipeline-stable-1.7.x/ci

It's work in progress. Concourse is still being evaluated and it may not be a good fit for us after all but so far I like what I'm seeing.

The biggest advantage is that every single bit of the pipeline is part of this pull request.

There is supporting infra that it's been configured manually for now.

• Server 1:
  • Concourse server
  • Concourse worker
  • PostgreSQL
  • Vault (secret management)
• Server 2:
  • Selenium Grid

The pipeline itself creates virtual machines in DigitalOcean to support different testing scenarios.

---

TODO:

• [ ] Leverage deploy-pub
• [ ] Build acceptance-tests image

Main goals not achieved yet:

• [ ] Pass acceptance tests in fresh installs
• [ ] Pass acceptance tests and rebuild indices in upgrades

Permutations ignored for now - not officially supported:

• pkg-ubuntu-16-04
• pkg-ubuntu-14-04 (known bug: @mamedin is working on it)
• ansible-centos-7 (known bug: nginx role needs to be pinned to v2.15)

[sevein]

Closing until I have time to get back to this. Currently working on running AMAUAT in our Compose envs.