Cleanup and consolidate the CI yaml docs (!4918) · Merge requests · GitLab.org / GitLab · GitLab

Achilleas Pipinellis - OOO until November 25th (parental leave) requested to merge docs/ci-yaml-cleanup-ee into master Mar 09, 2018

What does this MR do?

Port of https://gitlab.com/gitlab-org/gitlab-ce/merge_requests/17595