Allow users to set a number of instances of CEI services in launch

This allows users to launch multiple cei services on a VM in a launch. This will only work if ZK is enabled in the launch. To do so, add something like the following to your launch.yml

    basenodes:
      basenode:
        process_dispatcher:
          replicas: 2
        epum:
          replicas: 2
        provisioner:
          replicas: 2