Emit an event while in call for "ondevicechange"

[edolix]

To simplify the usage for the end-user, the BaseCall within the webrtc package could handle the native ondevicechange event and emit an SDK event that contains the "updated" device list or just the new device that has been plugged in (?)

But the ondevicechange event is fired for plugged/unplugged devices and, in some browsers, even when the deviceId and label becomes available (eg: after the first gUM).

Additional gUM/devices docs: #100

[framini]

Fixed by: #133 and #122