Update User Guide and Admin links to point to new resources. (#3438)

* Update links to outdated user-guide and admin docs

* Add script for updating outdated links.

* Update regex to include init-containers file.

* Pull upstream, rewrite links in and to namespaces walkthrough.

docs/tools/index.md

@@ -20,7 +20,7 @@ Kubernetes contains the following built-in tools:
 
 ##### Kubefed
 
-[`kubefed`](/docs/admin/federation/kubefed/) is the command line tool
+[`kubefed`](/docs/tutorials/federation/set-up-cluster-federation-kubefed/) is the command line tool
 to help you administrate your federated clusters.
 
 ##### Minikube
@@ -31,7 +31,7 @@ development and testing purposes.
 
 ##### Dashboard 
 
-[Dashboard](/docs/user-guide/ui/), the web-based user interface of Kubernetes, allows you to deploy containerized applications
+[Dashboard](/docs/tasks/web-ui-dashboard/), the web-based user interface of Kubernetes, allows you to deploy containerized applications
 to a Kubernetes cluster, troubleshoot them, and manage the cluster and its resources itself. 
 
 #### Third-Party Tools