DataChannel bandwidth test and WebRTCCall to help doing loopback calls.

Added WebRTCCall to help establishing a calling between two local peer connections.

Implemented a DataChannel bandwidth test that sends a block of packets of 1024 bytes
everytime the bufferedAmount is 0 and prints the bitrate sent over one second.
Did some alterations.. note that when using local network it is hard to see the event of bufferedAmount > 0 ... as so I placed a cap on the max number of packets we try to send before returning control to the JS event loop.