First pieces of lbaas api object model refactor

Added new loadbalancingv2 extension. Added new LoadBalancerPluginv2 class to plugin.py module. Added new loadbalancer_dbv2.py modules

Change-Id: I43270fdf9cd52a57274575ecea502f660ff0d5a9
Various improvements and fixes

Added test_and_set_status method so entities cannot be modified while in a
transitive state.
Implemented delete methods that were not implemented.
Various error checks.

Change-Id: I517493fb86b3202deaa2119bb4e0d2c9f5636fa6
Merge pull request #1 from brandonlogan/bp/lbaas-api-and-objmodel-improvement

Added new loadbalancerv2.py extension module.  Added new LoadBalancerPlu...