wifi: Allow configuration of country code for wifi

Wifi country code handling is a nightmare - Most retail devices
have region customization in /system for each country a device
is shipped to.

This doesn't work very well for a firmware like Cyanogenmod,
where we try to support all target countries with one firmware
package.  For whatever reason, with newer Broadcom drivers/
firmware blobs, the old trick of using a universal region code
(ccode=ALL in nvram_net.txt) does not seem to work.  Who knows
what the deal is for other wifi chipsets.

The good thing is that wpa_supplicant has a standardized
cross-chipset method for setting the region code, and we
use that here.

Change-Id: Ia9f5133f61f56d89ccb290e37a393f5de507e1cf
Wi-Fi: Manage Wi-Fi AP priorities

AOSP has a basic LRU priority for Wi-Fi networks (last connected has more priority).
This changes added the ability of graphically set the priority of any of the configured
Wi-Fi networks through Settings -> Wi-Fi -> Advanced Settings -> Wi-Fi priority.

Change-Id: Ief590e799cdb7ef760b631d0b22d9719f867393f
Signed-off-by: Jorge Ruesga <jorge@ruesga.com>