Dynamically add invoker post-deployment.

## Environment details:
It is a multiple controllers (HA), invokers distributed VM setup on ubuntu 14.04
How do we dynamically add a new invoker post deployment without dismantling existing one, in order to achieve auto-scaling ?
Any documentation / reference ?

Start with the OpenWhisk deployment documentation for multiple controllers and distributed VM invokers on Ubuntu 14.04. Verify whether a new invoker can be added without dismantling existing invokers and whether autoscaling is supported; done means a documented procedure or a clear statement of limitations.

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