User, Admin, and Developer guides.

First pass at organizing our docs for three separate audiences:
User, Cluster Admin, and developer.  Wrote a top-level guide
for each one, by selecting parts of the old docs/README.md.
The new docs/README.md mostly points to these 3 guides.

docs/cluster-admin-guide.md

@@ -0,0 +1,70 @@
+# Kubernetes Cluster Admin Guide
+
+The cluster admin guide is for anyone creating or administering a Kubernetes cluster.
+It assumes some familiarity with concepts in the [User Guide](user-guide.md).
+
+## Planning a cluster
+
+There are many different examples of how to setup a kubernetes cluster.  Many of them are listed in this
+[matrix](docs/getting-started-guides/README.md).  We call each of the combinations in this matrix a *distro*.
+
+Before chosing a particular guide, here are some things to consider:
+ - Are you just looking to try out Kubernetes on your laptop, or build a high-availability many-node cluster? Both
+   models are supported, but some distros are better for one case or the other.
+ - Will you be using a hosted Kubernetes cluster, such as [GKE](https://cloud.google.com/container-engine), or setting
+   one up yourself?
+ - Will your cluster be on-premises, or in the cloud (IaaS)?  Kubernetes does not directly support hybrid clusters.  We
+   recommend setting up multiple clusters rather than spanning distant locations.
+ - Will you be running Kubernetes on "bare metal" or virtual machines?  Kubernetes supports both, via different distros.
+ - Do you just want to run a cluster, or do you expect to do active development of kubernetes project code?  If the
+   latter, it is better to pick a distro actively used by other developers.  Some distros only use binary releases, but
+   offer is a greater variety of choices.
+ - Not all distros are maintained as actively.  Prefer ones which are listed as tested on a more recent version of
+   Kubernetes.
+ - If you are configuring kubernetes on-premises, you will need to consider what [networking
+   model](../../docs/networking.md) fits best.
+ - If you are designing for very [high-availability](availability.md), you may want multiple clusters in multiple zones.
+
+## Setting up a cluster
+
+Pick one of the Getting Started Guides from the [matrix](docs/getting-started-guides/README.md) and follow it.
+If none of the Getting Started Guides fits, you may want to pull ideas from several of the guides.
+
+One option for custom networking is *OpenVSwitch GRE/VxLAN networking* ([ovs-networking.md](ovs-networking.md)), which
+uses OpenVSwitch to set up networking between pods across
+  Kubernetes nodes.
+
+If you are modifying an existing guide which uses Salt, this document explains [how Salt is used in the Kubernetes
+project.](salt.md).
+
+## Upgrading a cluster
+[Upgrading a cluster](cluster_management.md).
+
+## Managing nodes
+
+[Managing nodes](node.md).
+
+## Optional Cluster Services
+
+* **DNS Integration with SkyDNS** ([dns.md](dns.md)):
+  Resolving a DNS name directly to a Kubernetes service.
+
+* **Logging** with [Kibana](logging.md)
+
+## Multi-tenant support
+
+* **Namespaces** ([namespaces.md](namespaces.md)): Namespaces help different
+  projects, teams, or customers to share a kubernetes cluster.
+
+## Security
+
+* **Kubernetes Container Environment** ([container-environment.md](container-environment.md)):
+  Describes the environment for Kubelet managed containers on a Kubernetes
+  node.
+
+* **Securing access to the API Server** [accessing the api]( accessing_the_api.md)
+
+* **Authentication**  [authentication]( authentication.md)
+
+* **Authorization** [authorization]( authorization.md)
+