Docs: Move tech articles to their topic-related directory

As discussed with @JobV, we'll move the technical articles to their topic-related directory:

• Pages articles are already placed in their correct dir
• Set up redirection https://gitlab.com/gitlab-com/gitlab-docs/merge_requests/167
  • Document redirection and dir structure => https://gitlab.com/gitlab-org/gitlab-ce/merge_requests/16327 + https://gitlab.com/gitlab-org/gitlab-ee/merge_requests/3976
• Move artifactory_and_gitlab => /ci/examples/ => https://gitlab.com/gitlab-org/gitlab-ce/merge_requests/16081 + https://gitlab.com/gitlab-org/gitlab-ee/merge_requests/3862
• Move how_to_configure_ldap_gitlab_ce and how_to_configure_ldap_gitlab_ee => /admin/auth/ => https://gitlab.com/gitlab-org/gitlab-ce/merge_requests/16094 + https://gitlab.com/gitlab-org/gitlab-ee/merge_requests/3866
• Move how_to_install_git => /topics/git/ => https://gitlab.com/gitlab-org/gitlab-ce/merge_requests/16322 + https://gitlab.com/gitlab-org/gitlab-ee/merge_requests/3973
• Move laravel_with_gitlab_and_envoy => /ci/examples/ => https://gitlab.com/gitlab-org/gitlab-ce/merge_requests/16359 + https://gitlab.com/gitlab-org/gitlab-ee/merge_requests/4000
• Move duplicate info for CI examples (https://gitlab.com/gitlab-org/gitlab-ce/issues/41872) => https://gitlab.com/gitlab-org/gitlab-ce/merge_requests/16372 + https://gitlab.com/gitlab-org/gitlab-ee/merge_requests/4008
• Move numerous_undo_possibilities_in_git => /topics/git/ => https://gitlab.com/gitlab-org/gitlab-ce/merge_requests/16365 + https://gitlab.com/gitlab-org/gitlab-ee/merge_requests/4089
• Move openshift_and_gitlab => /install/ => https://gitlab.com/gitlab-org/gitlab-ce/merge_requests/16367 + https://gitlab.com/gitlab-org/gitlab-ee/merge_requests/4004
• Move runner_autoscale_aws => /runner/configuration/ => https://gitlab.com/gitlab-org/gitlab-ce/merge_requests/16368 + https://gitlab.com/gitlab-org/gitlab-ee/merge_requests/4006 + gitlab-runner!805 (merged)
• Delete the content of /articles/index.md => https://gitlab.com/gitlab-org/gitlab-ce/merge_requests/16469 + https://gitlab.com/gitlab-org/gitlab-ee/merge_requests/4093

Context:

Deleting /articles/index.md needs moving all its articles first. A solid website structure is essential for SEO and for discoverability, that's why we're working on improving the entire structure of the docs with new index pages. As an example, see this page's breadcrumb: if you want to navigate back, there's no breadcrumb structure, so you land on /ee/readme. Now look at the breadcrumbs for this page: you can see the entire structure and navigate back to exactly where you want to.

cc/ @axil