Driver that integrates PlexxiCore with Congress

This driver integrates Plexxi's PlexxiCore Database into Congress. It pulls information stored about network elements such as Hosts and Virtual Machines and stores the acquired data in tables formatted in a relational style inside of congress. This Driver also incorporates a policy that can be enabled in configuration that works with the nova driver to enforce that no VM stored in the Plexxi Tables will have a name that matches with a VM stored inside the Nova tables demonstrating the ability to use congress to react to network changes and enforce policy.