Add ability to set media bit rate in rtc client

[bigsapper]

We are finding that we need to adjust the media bit rate in Chrome (b=AS:?).
http://www.rtcbits.com/2016/11/controlling-bandwidth-usage-in-webrtc.html
I've embedded the ability in the connect-rtc.js file.
https://webrtchacks.com/limit-webrtc-bandwidth-sdp/

I would prefer if the original project has this facility so that it can be called and set from an external client.

[bigsapper]

Adding that we have directly tried to apply media bitrate manipulation to the build file, and it doesn't look like the rtc isn't recognizing or honoring the settings.