first cut - configuring firewall edgegateway service
posting xml to configure nat service
adding optional fields for nat and firewall service
configuring load balancer service
element type is not required , when href is provided
renamed service post method according to documentation
broke generator code into smaller methods
moved method up in alphabetical order
using Camel case for edgegateway configuration
removed print statements added for debugging
Merge pull request #2260 from alphagov/configure_edge_gateway

[vcloud_director] Configure edge gateway services