Return a concise bridge JSON so that the bridge list loads faster.

Signed-off-by: Min Chen <minchnew@gmail.com>
Basic infos for a bridge has been changed to include the following:
Datapath ID, Fail Mode and OpenFlow Protocols.

Signed-off-by: Min Chen <minchnew@gmail.com>
Use $scope.br to save state changes. Modifications made to a bridge can be
viewed without having to go back to the bridge list page.

Signed-off-by: Min Chen <minchnew@gmail.com>