Apply maxVideoBW also to subscribers

[jcague]

Description

It enables the option to limit maxVideoBW in the subscriber side. It's really interesting for simulcast since two clients subscribed to the same publisher could have different max video bw without affecting the others.
A common use case happens when subscribers are connected from mobile phones and we don't want them to consume all their data traffic.

[] It needs and includes Unit Tests

Changes in Client or Server public APIs

We could only apply maxVideoBW to a publisher before this PR:

var config = {maxVideoBW: 300};
localstream.updateConfiguration(config, function(result) {
  console.log(result);
});

But now we can also set the maxVideoBW to remoteStreams:

var config = {maxVideoBW: 300};
remoteStream.updateConfiguration(config, function(result) {
  console.log(result);
});

• It includes documentation for these changes in /doc.

[lodoyun]

LGTM!