Add Openshift Docs

[ozdanborne]

Calico's openshift-ansible integration is close to being merged.

We need a docs landing page and resources for people coming from the readme's over there.

For a small increment, it could just be a landing page and explanation of which Kubernetes docs / concepts apply.

Longer term we need:

• Explanation of integration with openshift components
• Custom walkthroughs using oc CLI

Proposed layout:

Path	Description
/getting-started/openshift/installation/index.md	Cover how to use ansible installs
/getting-started/openshift/tutorials/simple-policy.md	The simple policy demo for openshift

[ozdanborne]

This was merged in #816