Support for batched configure requests in VideoRoom

[lminiero]

The configure request in the VideoRoom plugin can be used for different purposes, e.g., pausing/resuming streams, choosing simulcast layers, etc. So far, since we merged multistream, this was a drilldown request, meaning you had to specify the mid to act upon: this also meant that if you wanted to make multiple changes on different m-lines at the same time, you had to send different configure requests.

This PR addresses that by adding a batched mode to configure instead, where you pass a stream called arrays with all the individual changes you want to make, e.g.:

subscription.send({message: {request: "configure", streams: [{mid: "0", send: true}, {mid: "1", send: true}]}})

I've tested this briefly and it seems to work as expected, but of course more feedback would be helpful. Pinging @mirkobrankovic in particular as he expressed interested in something like this a few days ago.

[lminiero]

Merging.