Add Linkerd as add-on

[alexellis]

Add Linkerd as add-on

Expected Behaviour

It'd be great to be able to pick linkerd_enable: true in init.yaml or something similar to that and have it download their CLI, and bootstrap, then inject the appropriate headers for the edge-router ingress to enable TLS, including the inject statements for the openfaas-fn namespace etc

As per - https://github.com/openfaas-incubator/openfaas-linkerd2

Current Behaviour

As of now it's being done manually by the operator

Possible Solution

If enabled, check for the binary at start-up time, then use the linkerd CLI as per the guide above.

[Waterdrips]

/assign: me