Add a couple of new flags to Warden CLI which allows doing bulk jail
creation!

Using the --bulk <number> and --ip4pool <starting address> flags you can
now create multiple jails at once, using the starting IP address you specify

Warden will check the jail nickname / ip address and sure that they don't
already exist on the host, and if so it'll skip and continue to the next
IP / nickname available in the pool