Basic multi-cluster support

[libby]

Initial support for running a quorum k8s network across multiple clusters.

To run a multi-cluster Quorum k8s network, a quorum network must initially be started in a single cluster and the genesis.json needs to be shared with all other cluster that wish to connect.

There is a new (optional) entry in the qubernetes config external-nodes, e.g.

external_nodes:
  - Node_UserIdent:  quorum-node1
    Tm_Url:  192.168.64.49:30853
    Enode_Url: "enode://e6ccd013b90e17ea7692905609f2a8a7922d855ebcb4476f1afc6aa4ad4261a2af40df9f1b6f4c6a83c96fd40bbad4d63352047d890a278d6cd410a225a1a236@192.168.64.49:31500?discport=0&raftport=50401"
    Node_Acct_Addr: "0xC7868aA6C261aAaDA3E370315B6CF752056F54d1"
  - Node_UserIdent:  quorum-node2
    Tm_Url:  192.168.64.49:31680

This is the information that a cluster needs to connect to another cluster. There is a qctl command to obtain this info from inside a cluster, e.g. qctl ls nodes --asexternal -b --node-ip=$(minikube ip)

If cluster A (C-A) wishes to add nodes from cluster B (C-B), C-A must:

1. Obtain its running node information as an external node, e.g. qctl ls nodes --asexternal -b --node-ip=$(minikube ip) and give this it C-A.
2. C-A must add C-B's external_node info to its qubernetes config and generate the appropriate resources, qctl generate network --update.
3. Once C-A has been deploy, C-A must do the same: obtain the external_nodes info for its running nodes, and share that with C-B.
4. When C-B has updated its qubernetes config with C-A external_nodes and redeployed, the nodes should be able to connect.

• note: currently only supporting NodePort so the external_node info must be obtained from a running cluster, and note the NodePort may change if the node goes down.
• todo: Ingress support should be implemented next, so that the external_node info will not change if a node goes down and is restarted.