Ref #697

Extensively discussed during our 2018-05-14 community/team call (http://minutes.iiab.io).

Please contact @jvonau @tim-moody @georgejhunt for details, e.g. :

• Android/Windows/Apple client implications (e.g. are resolvable box.local and Avahi important?)
• default channel 6 in local_vars.yml that can be overriden by upstream channel?
• @jvonau initial results appear very reliable so far
• test+fix explorations to hammer out common/corner cases...

raspi-config (CLI menuing tool to set RPi's internal SSID & password/PSK) can be modified to work with wpa_supplicant approach as follows: (thanks to @jvonau)

list_wlan_interfaces() {
#  for dir in /sys/class/net/*/wireless; do
  for dir in /sys/class/net/wlan0/wireless; do