Add WLAN support.

### States

#### Common

##### WLAN

* Execute `common.wlan` to setup wireless LAN on the RNAs. The devices automatically connect to the LARN network.

* Check for present WLAN networks: `sudo iwlist wlan0 scan | grep ESSID`

#### Demo

* Execute `demo.control` to deploy the control demo.

auto wlan0

allow-hotplug wlan0

iface wlan0 inet manual

wpa-conf /etc/wpa_supplicant/wpa_supplicant.conf

network={

	ssid="LARN"

	scan_ssid=1

	key_mgmt=WPA-PSK

	psk="larn2018"

}

# WPA-EAP - Example

# network={

#   ssid="eduroam"

#   scan_ssid=1

#   key_mgmt=WPA-EAP

#   identity="USER"

#   password="PASSWORD"

#   eap=PEAP

#   phase1="peaplabel=0"

#   phase2="auth=MSCHAPV2"

# }

wpasupplicant:

    pkg.installed

network_interfaces:

    file.managed:

        - name: /etc/network/interfaces.d/wlan0

        - source: salt://common/files/wlan0

wpa_supplication.conf:

    file.managed:

        - name: /etc/wpa_supplicant/wpa_supplicant.conf

        - source: salt://common/files/wpa_supplicant.conf