Add LB Balancer Cluster class
user
```ruby
require 'stacks/namespace'
require 'stacks/machine_def_container'
require 'stacks/app_server'
require 'stacks/nat'
require 'uri'

module Stacks::LoadBalancerCluster

  def self.extended(object)
    object.configure()
  end

  def configure()
  end

  def depends_on
    virtual_services(Stacks::AbstractVirtualService).map do |machine|
      machine.name
    end
  end

  def virtual_services(type)
    virtual_services = []
    environment.accept do |node|
      unless node.environment.contains_node_of_type?(Stacks::LoadBalancer) && environment != node.environment
        virtual_services << node if node.kind_of? type
      end
    end
    virtual_services
  end

  def clazz
    return 'loadbalancercluster'
  end
end
```
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