Separated user, dev, and design docs.

Renamed: logging.md -> devel/logging.m
Renamed: access.md -> design/access.md
Renamed: identifiers.md -> design/identifiers.md
Renamed:    labels.md -> design/labels.md
Renamed:    namespaces.md -> design/namespaces.md
Renamed:    security.md -> design/security.md
Renamed:    networking.md -> design/networking.md

Added abbreviated user user-focused document in place of most moved docs.

Added docs/README.md explains how docs are organized.
Added short, user-oriented documentation on labels
Added a glossary.
Fixed up some links.

docs/README.md

@@ -0,0 +1,29 @@
+# Kubernetes Documentation
+
+Kubernetes documentation is organized into several categories.
+
+  - **Getting Started Guides**
+    - for people who want to create a kubernetes cluster
+    - in [docs/getting-started-guides](./getting-started-guides)
+  - **User Documentation**
+    - in [docs](./overview.md)
+    - for people who want to run programs on kubernetes
+    - describes current features of the system (with brief mentions of planned features)
+  - **Developer Documentation**
+    - in [docs/devel](./devel)
+    - for people who want to contribute code to kubernetes
+    - covers development conventions
+    - explains current architecture and project plans
+  - **Design Documentation**
+    - in [docs/design](./design)
+    - for people who want to understand the design choices made
+    - describes tradeoffs, alternative designs
+    - descriptions of planned features that are too long for a github issue.
+  - **Walkthroughs and Examples**
+    - in [examples](../examples)
+    - Hands on introduction and example config files
+  - **API documentation**
+    - in [api](../api)
+    - automatically generated REST API documentation
+  - **Wiki**
+    - in [wiki](https://github.com/GoogleCloudPlatform/kubernetes/wiki)