Refactor WiFi scan example

[Erriez]

I've refactored the WiFi scan example with better readable output:

ESP8266 WiFi scan example
Starting WiFi scan...
10 networks found:
  00: [CH 01] [XX:XX:XX:06:4B:E7] -88dBm * V xxxxxxxxxxx
  01: [CH 01] [XX:XX:XX:F8:C2:C1] -94dBm * V xxxxxxxxxx
  02: [CH 01] [XX:XX:XX:09:6C:21] -89dBm * V xxxxxxx
  03: [CH 04] [XX:XX:XX:10:B8:12] -89dBm * V xxxxxxxxxxxxxx
  04: [CH 01] [XX:XX:XX:F8:C2:C1] -92dBm * V xxxxxxx
  05: [CH 06] [XX:XX:XX:2F:4C:68] -75dBm * V xxxx
  06: [CH 01] [XX:XX:XX:09:6C:21] -90dBm * V xxxxxxxxxxxxxx
  07: [CH 11] [XX:XX:XX:89:4E:8F] -90dBm * V xxxxxxxxxxxx
  08: [CH 11] [XX:XX:XX:34:0E:E0] -69dBm * H
  09: [CH 01] [XX:XX:XX:64:AC:1F] -90dBm * V xxxx
Starting WiFi scan...
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