opendingux: Add configuration scripts for wlan interfaces

Provided the file /etc/local/network/config-wlan[0-9].conf is present,
running "ifup wlan[0-9]" will configure the wireless interface (set
the ESSID, encryption method and passphrase), and obtain an IP address
automatically, according to the config options.

Running "ifdown wlan[0-9]" will de-configure the interface, and kill
the corresponding wpa_supplicant and udhcpc daemons.
opendingux: Prevent udev from configuring wireless interfaces

This is an embedded system; the user should decide when to start
and stop wireless interfaces, to not waste too much power.