Support multiple OR addresses
The data formats allow including more than one OR address, but the server doesn't implement that yet. It doesn't need to, because neither the bridge authority nor the directory authority publish a relay's second OR address yet. But once that changes we should include all OR addresses in the documents.
As a side-effect, OR ports may then be port lists. Using an int to represent an OR port will not work anymore.
Once we support IPv6 OR addresses, we'll also want to support searching for IPv6 addresses.
(This was issue 5 in my GitHub repository.)