runconfig: add -net container:name option

usage:
```
docker run -net container:name_or_id
docker run -net bridge
docker run -net disable
```

Example:
```
proppy@noir:~/mygo/src/github.com/dotcloud/docker$ bundles/0.10.0-dev/binary/docker-0.10.0-dev -H :4244 run -d -name netcat_server aanand/netcat nc -l 9999
Warning: '-name' is deprecated, it will be replaced by '--name' soon. See usage.
6a1573e9033810c71c3b28a1a4e34f6b10ab8add0437d6943a60a85279cc881c
proppy@noir:~/mygo/src/github.com/dotcloud/docker$ bundles/0.10.0-dev/binary/docker-0.10.0-dev -H :4244 ps
CONTAINER ID        IMAGE                  COMMAND             CREATED             STATUS              PORTS               NAMES
6a1573e90338        aanand/netcat:latest   nc -l 9999          4 seconds ago       Up 4 seconds                            netcat_server       
proppy@noir:~/mygo/src/github.com/dotcloud/docker$ bundles/0.10.0-dev/binary/docker-0.10.0-dev -H :4244 run -net container:netcat_server aanand/netcat bash -c 'echo coucou | nc localhost 9999'
Warning: '-net' is deprecated, it will be replaced by '--net' soon. See usage.
proppy@noir:~/mygo/src/github.com/dotcloud/docker$ bundles/0.10.0-dev/binary/docker-0.10.0-dev -H :4244 logs netcat_server
coucou
```

Related: #4441