JSEP: ICE candidate generation and association with sessions

One thing that's not clear to me in the JSEP proposal:

In the case where we don't have a single RTP session, there has to be 
candidates generated for all sessions.

The job of putting the a=candidate lines into the SDP description is 
left to the JS (or a JS library), which means that we need to associate 
candidates with the right m= line.

Suggestion: Add some parameters....

pc.connect() -> pc.startIce(number of sessions)
iceCallback(candidate) -> iceCallback(session index, candidate)

where "index" is a number between 0 and "number of sessions" - 1.

There are probably more ways to do this. This was the simplest I could 
think of.

                  Harald