ovn: Design and Schema changes for Container integration.

ovn: Design and Schema changes for Container integration.

The design was come up after inputs and discussions with multiple
people, including (in alphabetical order) Aaron Rosen, Ben Pfaff,
Ganesan Chandrashekhar, Justin Pettit, Russell Bryant and Somik Behera.

Signed-off-by: Gurucharan Shetty <gshetty@nicira.com>
Acked-by: Russell Bryant <rbryant@redhat.com>
Acked-by: Ben Pfaff <blp@nicira.com>