Merge pull request #102 from midokura/ryu/MN-1725

SG API support
Merge pull request #103 from midokura/ryu/MN-1729

New MidoNet router API support
router interface add/remove support

Implement router interface add and remove Neutron API that
make corresponding requests to the MidoNet API.

Implements: MN-1732
Signed-off-by: Ryu Ishimoto <ryu@midokura.com>