Authentication subsection renamed to Security (#496)

* split tasks into categories

* redirects

* Update istio-auth.md

* Update rate-limiting.md

* Update distributed-tracing.md

* fix links

* nit

* FAQs

* enable cujs

* remove draft

* more nits per feedback

* upgrading istio

_docs/samples/upgrading-istio.md

@@ -0,0 +1,30 @@
+---
+title: Upgrading Istio
+overview: This guide demonstrates how to upgrade the Istio control plane and data plane independently.
+
+order: 70
+
+layout: docs
+type: markdown
+---
+{% include home.html %}
+
+This guide demonstrates how to upgrade the Istio control plane and data plane independently.
+
+## Before you begin
+* Describe installation options.
+
+* Install Istio control plane in a Kubernetes cluster by following the quick start instructions in the
+[Installation guide]({{home}}/docs/setup/install-kubernetes.html).
+
+## Overview
+
+Placeholder.
+
+## Application Setup
+
+1. Steps
+
+## Tasks
+
+1. some tasks that will complete the goal of this sample.

_docs/tasks/security/index.md

@@ -1,5 +1,5 @@
 ---
-title: Authentication
+title: Security
 overview: Describes tasks that help securing the service mesh traffic.
 
 order: 20