Add option to advertise relay addresses along with other addresses

[whyrusleeping]

Currently, if we want to advertise relay addresses, we have to specify all the addresses we want to advertise in the Addresses.Announce config field (because that field correctly replaces all addresses instead of augmenting them). We should have a way to either say "Add relay addresses to my list of addresses that I announce!" or "add this set of addresses to the list of addresses that I announce".
I'm leaning towards the relay specific option, but opinions are welcome.

[grokcoder]

Hello, I am glad to help this issue. Do you want a more conveniont way to manipulate the relay addrs?
How about to add some command like

ipfs announce list // list the announce addr
ipfs announce add <addr>
ipfs announce rm <addr>

[bigs]

@grokcoder @whyrusleeping i can get started on this tomorrow. i'd likewise favor the specific option since the less specific option can be built atop it!