Add L4LB resources to midonetclient

This patch adds resources specified in our L4LB specification to
midonetclient.

Signed-off-by: Taku Fukushima <tfukushima@midokura.com>
Add L4LB resources to MidonetApi and Application.

This patch adds the connections between the application and the L4LB
resources added by the previous patch.

Signed-off-by: Taku Fukushima <tfukushima@midokura.com>
Add the support of the L4LB feature to midonet-cli

This patch adds the commands for the L4LB featrue to midonet-cli.

Signed-off-by: Taku Fukushima <tfukushima@midokura.com>