VTEP binding deletion CLI

Makes VTEP and VTEP bindings aliased, and allows referencing them via
aliases for show / list / delete commands.

Sample command lines:
midonet> list vtep
vtep vtep0 name br0 management-ip 119.15.112.22 management-port 6633 connection-state CONNECTED
midonet> vtep vtep0 show management-ip
119.15.112.22
midonet> vtep vtep0 list binding
binding binding0 management-ip 119.15.112.22 physical-port Te 0/2 vlan 908 network-id bc3afc36-6274-4603-9109-c29f1c12ba33
binding binding1 management-ip 119.15.112.22 physical-port Te 0/2 vlan 439 network-id bc3afc36-6274-4603-9109-c29f1c12ba33
binding binding2 management-ip 119.15.112.22 physical-port Te 0/2 vlan 777 network-id bc3afc36-6274-4603-9109-c29f1c12ba33
binding binding3 management-ip 119.15.112.22 physical-port fakevm1_out vlan 0 network-id 7071b156-5f05-4d8c-8df2-3bb22a9325fc
binding binding4 management-ip 119.15.112.22 physical-port in1 vlan 119 network-id 1d475afc-d892-4dc7-af72-9bd88e565dde
midonet> vtep vtep0 binding binding4 show vlan
119
midonet> vtep vtep0 binding binding4 delete
midonet>

Fix MN-1824
Thank you Guillermo for the detailed discussion. As you pointed out, Python Client is structured so that the top-level resource would have all the getters. That makes sense as a design decision. It's a separate discussion how the MidoNet Rest resources should be structured, and to be honest, I'm not sure if there's consistency in the way it is currently structured. It seems to need some re-alignment now.