make `weave attach|expose|detach|hide` show IP addresses
make `weave attach|expose|detach|hide` show IP addresses

The output contains one IP address for each addr (i.e. [ip:]<cidr> |
net:<cidr> | net:default) supplied on the command line; or, if none
was specified, a single address from the default IPAM subnet.

We don't want `weave run` to output the addresses, since it is meant
to (only) output the container id. Hence we redirect the `attach`
output to stderr in that case.

Closes #954.

BWITS/weave,kidaa/weave,squaremo/weave,OnePaaS/weave,awh/weave,paulbellamy/weave,tomwilkie/weave,aaam/weave,awanke/weave,rade/weave,n054/weave,achanda/weave,weaveworks/weave,squaremo/weave,beni55/weave,squaremo/weave,achanda/weave,errordeveloper/weave,ycaihua/weave,cgvarela/weave,bboreham/weave,paladin74/weave,cgvarela/weave,OnePaaS/weave,paladin74/weave,ycaihua/weave,kidaa/weave,philipz/weave,bboreham/weave,awanke/weave,n054/weave,beni55/weave,errordeveloper/weave,2opremio/weave,awanke/weave,squaremo/weave,aaam/weave,BWITS/weave,achanda/weave,weaveworks/weave,tomwilkie/weave,awh/weave,narry/weave,paladin74/weave,weaveworks/weave,dpw/weave,bboreham/weave,awanke/weave,bboreham/weave,kidaa/weave,philipz/weave,2opremio/weave,achanda/weave,aaam/weave,2opremio/weave,rade/weave,aaam/weave,OnePaaS/weave,narry/weave,beni55/weave,dpw/weave,n054/weave,paulbellamy/weave,2opremio/weave,errordeveloper/weave,paladin74/weave,2opremio/weave,paulbellamy/weave,tomwilkie/weave,awh/weave,OnePaaS/weave,dpw/weave,squaremo/weave,ycaihua/weave,rade/weave,OnePaaS/weave,kidaa/weave,ycaihua/weave,beni55/weave,narry/weave,paladin74/weave,cgvarela/weave,rade/weave,awh/weave,weaveworks/weave,paulbellamy/weave,rade/weave,dpw/weave,philipz/weave,aaam/weave,cgvarela/weave,ycaihua/weave,tomwilkie/weave,dpw/weave,tomwilkie/weave,errordeveloper/weave,beni55/weave,n054/weave,awh/weave,philipz/weave,BWITS/weave,errordeveloper/weave,achanda/weave,narry/weave,narry/weave,cgvarela/weave,BWITS/weave,bboreham/weave,philipz/weave,BWITS/weave,kidaa/weave,n054/weave,awanke/weave