lib/ovs: add constants for ovsdb Open_vSwitch db

Those constants are used to manipulate Open_vSwitch db of ovsdb.

Signed-off-by: Isaku Yamahata <yamahata@valinux.co.jp>
Signed-off-by: FUJITA Tomonori <fujita.tomonori@lab.ntt.co.jp>
lib/ovs/vsctl: python reimplementation of ovs-vsctl

This implements subset of ovs-vsctl which is used later.

Signed-off-by: Isaku Yamahata <yamahata@valinux.co.jp>
Signed-off-by: FUJITA Tomonori <fujita.tomonori@lab.ntt.co.jp>
lib/ovs/bridge: helper class to manipulate ovs bridge

Signed-off-by: Isaku Yamahata <yamahata@valinux.co.jp>
Signed-off-by: FUJITA Tomonori <fujita.tomonori@lab.ntt.co.jp>