Make it possible to skip the UDP broadcast in the reccaster

[jacomago]

UDP Broadcasts are being a problem more and more, we should be able to specify the hostname or ip address in the reccaster configuration. That way we skip the look for recceiver.

[mdavidsaver]

Broadcasts are being a problem more and more

... for those running containers with virtual networking?

Still, for such situations I think it would be reasonable to take a list of server name/IPs in an environment variable. eg. RECSYNC_ADDR_LIST. These endpoints would be tried in a round-robin fashion, perhaps with a random starting point.