Split Jenkins docs
What does this MR do?
Refactor Jenkins docs a bit.
Replaces https://gitlab.com/gitlab-org/gitlab-ee/merge_requests/169
Edited by Achilleas Pipinellis
Do not update/delete: Banner broadcast message test data
Do not update/delete: Notification broadcast message test data
Refactor Jenkins docs a bit.
Replaces https://gitlab.com/gitlab-org/gitlab-ee/merge_requests/169