`skywire-cli visor ip` subcommand

[0pcom]

you are using the vpn and you want to check from command line what your IP address is.

We should have this as a flag in skywire-cli.

skywire-cli visor ip --lan

this should return the LAN ip address of the running visor.

skywire-cli visor ip --inet 

this should return the public / internet ip address of the running visor.

We can query ip.skycoin.com for the internet / public ip address (?)

[jdknives]

@0pcom we already have the public IP in most cases from the NAT check. So should be simple enough to return it here via CLI.

[0pcom]

added in #1475