Add proper authentication

[radu-matei]

This will use the in-cluster configuration of the Kubernetes client and the bot will make internal requests to the client.

We need to add proper authentication - decide the best strategy for this - Microsoft account, .kubeconfig or something else.

For now, in-cluster authentication will suffice.

[radu-matei]

Authentication will be similar to the Cortana Skills demo at Build, by registering the bot to use the Microsoft account.

The question is regarding integration with Kubernetes RBAC? First I assume it will be a config file that will hold the account and permissions.