auto-attach: Add auto-attach support to bridge layer and command set

auto-attach: Add auto-attach support to bridge layer and command set

This is the final commit in the series of commits that deliver initial support
for Auto-Attach. Specifically this commit delivers auto-attach support to the
OVS bridge layer as well as the new auto-attach commands. The OVSDB schema is
modified to define the new auto-attach entries. The man pages, unit tests, and
news and license notice files are also updated. A unit test is provided to
validate the construction of auto-attach packets.

Signed-off-by: Ludovic Beliveau <ludovic.beliveau@windriver.com>
Signed-off-by: Dennis Flynn <drflynn@avaya.com>
Signed-off-by: Ben Pfaff <blp@nicira.com>