Support deploying IPv6 address

[Wouter0100]

Currently we define the IPv4 address ID in spec.loadBalancerIP, but I think we should make that field comma-separated?

Or: introduce a separate annotation, since loadBalancerIP is deprecated either way.

[ivard]

This is really a must-have feature for customers that want to use Kubernetes and want to comply with modern internet standards. It's fine to have a IPv4-only network inside the Kubernetes cluster itself, but we do want the load balancer to be reachable over IPv6. The load balancer could convert IPv6 to IPv4 to send it to the cluster.

I think the functionality has been implemented already in the load balancers, so the only think that is missing in my view is a way to request this feature using the Kubernetes API. There should be a load balancer annotation to request this setting.