New CI YAML features

This introduces a couple of small `.gitlab-ci.yml` features:

1. Documentation for: Allow to use YAML anchors when parsing the `.gitlab-ci.yml`: https://gitlab.com/gitlab-org/gitlab-ce/merge_requests/2958
2. Ignore jobs that start with `.`
3. Allow to pass name of created artifacts archive in `.gitlab-ci.yml`
4. Allow to define on which builds the current one depends on

These are really small changes so it makes not sense to create a separate merge requests for them.

@axil Could you review the documentation part?

The implementation on GitLab Runner side: https://gitlab.com/gitlab-org/gitlab-ci-multi-runner/merge_requests/113.

Fixes: https://gitlab.com/gitlab-org/gitlab-ce/issues/13755 https://gitlab.com/gitlab-org/gitlab-ce/issues/14211 https://gitlab.com/gitlab-org/gitlab-ce/issues/3423

cc @grzesiek @axil @DouweM 


See merge request !3182