Adding NSX API support in NSX integration

We would like to have fully automated process of NSX integration, including registration of compute nodes in NSX Manager.

To have it we would like to implement NSX API commands in barclamp-neutron
Some example:
- https://github.com/cloudbau/chef-nvp

This change (and the few below) seem unrelated to what you were doing here. Would it make sense to split them in another commit? The rationale for the change is not documented, so would be good to do so in the commit message :-)