reactive ui with client-node and kubectl proxy

[juozasg]

This update adds support for client-node javascript kubernetes client to show real-time view of the cluster resources. Whenever possible the js client is used, if it's not available, the extension will safely fallback to the kubectl get method for querying cluster state. The new system is labeled with k8s prefix while the old system is called kubectl get or kubernetesTools.

The javascript client requires kubectl proxy process to be running to be authenticated to the server. The update extension watches and restarts the kubectl proxy process as needed. Everything is reload when users click the "Refresh" buttons. Caching for namespaces is added. As much as possible all types used by the extension are moved to use client-node types, which are prefixed with k8s