Integration with OVS and Hardening of APIs

- Tested complex scenarios such as deleting SF from chain,
  deleting data plane locator, deleting SF, adding SF, etc

- Updated models as needed based on code and tests

- Implemented southbound REST communication and
  tested OVS integration

Change-Id: Icfba656babd566ee82b0c1ec17bf7ba4fb154989
Signed-off-by: Reinaldo Penno <rapenno@gmail.com>