Configurable ports when service type is NodePort

[Jhoyola]

For a simple and static way to connect to the node RPCs from host machine, the service type can be set to "NodePort". This PR makes it possible to fix static ports for each node to preconfigure a development environment based on warnet.

[pinheadmz]

I think mechanically this is the right choice to get remote access to each pod individually. It seems more correct and kubernetes-y than #686 which addresses the same goal.

Questions:

• How does the local user get the IP:port of the pod they want to connect to?
• How does this work in a large scale cluster with multiple kubernetes nodes, multiple pods on each node?

[Jhoyola]

• How does the local user get the IP:port of the pod they want to connect to?

User would add the below to the node on their network configuration. Then it's accessible at localhost:30443. I added documentation about this. Also added a small section about kubectl port-forward similar to #686 but without a warnet command.

    service:
      type: NodePort
      rpcNodePort: 30443

• How does this work in a large scale cluster with multiple kubernetes nodes, multiple pods on each node?

Haven't tested it, but according to Kubernetes docs it works just as: <kubernetes-node-ip>:<exposed-port>