Feature request: use an existing Ingress controller

[khos2ow]

Expected Behaviour

I want to use ofc-bootstrap against an existing and configured cluster, which already has ingress controller installed and configured on it. But ofc-bootstrap is always going to install ingress-controller. I'd like to be able to:

1. make the installation of ingress controller optional
2. override value of kubernetes.io/ingress.class annotation (to be completely flexible)
3. pass additional annotations to ingress controller

Current Behaviour

None of the above.

[alexellis]

Same as my comment on the other issue. It's probably best not to raise issues for every idea you have thought of right now, and instead discuss with the community on Slack.

The main reason is that we are currently migrating the setup and some of your requests won't apply afterwards.

[alexellis]

/set title: Feature request: use an existing Ingress controller