esp8266/modnetwork: Allow to configure STA and AP interfaces separately.
On ESP8266, there're 2 different interfaces. Pretending it's not the case desn't make sense. So, network.WLAN() now takes interface id, and returns interface object. Individual operations are then methods of interface object. Some operations require i/f of specific type (e.g. .connect() makes sense only for STA), other are defined for any (e.g. .ifconfig(), .mac()).