[add] add smartconfig support

[lapsule]

Add smartconfig support to modnetwork, here is a demo:

import network
wlan = network.WLAN(network.STA_IF)
wlan.active()
wlan.smartconfig()

[dpgeorge]

Thanks for the contribution. Is smartconfig a standard supported by more than one device, or is it an ad-hoc thing? If it's ESP specific then it should go in the esp module. Also, a lot of your code looks copied from somewhere else, which means you can't submit it just like that.