The following fixes were needed to make this happen. All of these things
are valid, I just made assumptions/used Chromium default values.
* Drop the sessionId to 32bits (from 64)
* When generating a response use the same mid values as the offer
* Use the localDescription to map a payloadType to video codec
Candidates are now generated with real priority, and actually pay
attention to the inbound messages.
Next we just need to pluck use-candidate + ice-controlling from the
messages and we will have a full-ice implementation (but we are not
controlling)
We then need to add timers to alert when the peer goes away OR when we
need to send again.
