Setup a default allow-all Pod Security Policy in Kubernetes API server

[JunSun17]

Is this a request for help?: No

Is this an ISSUE or FEATURE REQUEST? (choose one): Feature

Orchestrator and version (e.g. Kubernetes, DC/OS, Swarm): Kubernetes

What you expected to happen: For security concerns and auditing requirement, we should setup a Pod Security Policy for Kubernetes API server, and users should be able to modify it to apply their customization.

[stale]

This issue has been automatically marked as stale because it has not had recent activity. It will be closed if no further activity occurs. Thank you for your contribution. Note that acs-engine is deprecated--see https://github.com/Azure/aks-engine instead.