add support for add/remove of networks to vms

this allows adding and removing of nics to vms. Really needs a `knife cs server listnics` to go along with it so folks can get the uuids of the nics for deletion. Both calls, however, work with uuids:

```
» knife cs server add nic 28d4f061-30ed-4589-835b-df7c279f7863 ec5f314d-0413-417c-9485-f0c9627a2e7d
..
Server         Network                Type      Default  Address       Gateway     Netmask        ID
i3-nrouter-02
               prod-isolated-network  Isolated  true     172.16.2.173  172.16.2.1  255.255.255.0  a0386da2-a472-41ef-a174-e2017facfd35
               trial-network          Isolated  false    172.16.3.217  172.16.3.1  255.255.255.0  ec5f314d-0413-417c-9485-f0c9627a2e7d
```
```
» knife cs server remove nic 28d4f061-30ed-4589-835b-df7c279f7863 2559b2c2-8f34-4ce5-9283-c805b96255ea
..
Server         Network                Type      Default  Address       Gateway     Netmask        ID
i3-nrouter-02
               prod-isolated-network  Isolated  true     172.16.2.173  172.16.2.1  255.255.255.0  a0386da2-a472-41ef-a174-e2017facfd35
```

```
» knife cs server add nic 28d4f061-30ed-4589-835b-df7c279f7863 ec5f314d-0413-417c-9485-f0c9627a2e7d --ipaddress 172.16.3.2
..
Server         Network                Type      Default  Address       Gateway     Netmask        ID
i3-nrouter-02
               prod-isolated-network  Isolated  true     172.16.2.173  172.16.2.1  255.255.255.0  a0386da2-a472-41ef-a174-e2017facfd35
               trial-network          Isolated  false    172.16.3.2    172.16.3.1  255.255.255.0  ec5f314d-0413-417c-9485-f0c9627a2e7d
```