Modified the snowflake client to use pion/webrtc as the webrtc library.
This involved a few small changes to match function signatures as well
as several larger ones:
- OnNegotiationNeeded is no longer supported, so CreateOffer and
SetLocalDescription have been moved to a go routine called after the
other peer connection callbacks are set
- We need our own deserialize/serialize functions
- We need to use a SettingEngine in order to access the
OnICEGatheringStateChange callback

 - stabilize rest of WebRTCPeer
 - use uid for the datachannel label
 - store a consistent WebRTC config in the dialer

maxedChan

retry client offers immediately instead of reset, combine sendOffer and receiveAnswer into exchangeSDP

remove webRTCConn SendLoop and simplify Write without additional channel, as net.Conn is already safe

clean up ice candidate log message.
still need to debug the copy loop break.

log traffic bytes only once every few seconds, along with OnMessage & datachannel.Send counts, to prevent flooded logs