add options for disabling the default listen address/transports
add options for disabling the default listen address/transports

So, in go-ipfs at least, we *don't* pass the listen addresses into the libp2p
constructor. Instead, we specify them later.

This option allows us to tell libp2p to not listen by default.

libp2p/go-libp2p,libp2p/go-libp2p,ipfs/go-libp2p