Import and test our old OpenShift blog post into CE documentation

Description

We need this old blog post https://about.gitlab.com/2016/06/28/get-started-with-openshift-origin-3-and-gitlab/ on installing GitLab on Openshift imported into our CE documentation. The copy does not have to be rewritten only updated, most of the work will be:

• testing the existing the setup steps and updating them where necessary
• updating screenshots

For related content see our recent video:

https://about.gitlab.com/2017/05/16/devops-containers-gitlab-openshift/

and these guides on OpenShift's site:

• https://blog.openshift.com/deploy-gitlab-openshift/
• https://blog.openshift.com/code-test-deploy-with-gitlab-on-openshift-commons-briefing-49/

Issue first raised in https://gitlab.com/gitlab-org/gitlab-ce/issues/32388

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