EdgeGateway LoadBalancer generator working for Pools

Relatively complete input syntax to Fog/vCloud load balancer pools section.

This still needs validating against a live instance though - the output section
of the test is mostly correct, but needs confirmation and refinement.
EdgeGateway generator working for VirtualServer

not entirely complete, but enough until we can validate test output against API
include load_balancer_service schema
Rejig EdgeGatewayServices to handle each service

* diff now returns a hash of services, with the HashDiff array
  under each key.
* integration tests are passing for NatService and FirewallService
* pre-emptive work ready for coupling up LoadBalancerService
Enable LoadBalancerService

* integration tests failing at the moment, need to refine the generator
fixes to LoadBalancer generator

... to reflect requirements of API

Mostly working now, with the exception of the Interface section requires
that we look up the name from the network ID.
look up network name via Core::EdgeGateway
more corrections to LoadBalancerService tests
fix up LoadBalancer generator test

* minor corrections based on knowledge of API behaviour
* account for requiring EdgeGateway
Service-specific differ classes

So that we can, in the case of LoadBalancerService, handle the fact that we
get {Operational: false} returned by the API - we need to strip this out
of the remote config before comparing.

In this commit, the diff behaviour is not changed - HashDiff is used as before.