wpadebug: Add support for QR Code scanning and display via zxing

wpadebug: Add support for QR Code scanning and display via zxing

Enhance wpadebug application to support scanning and displaying of QR
codes. This depends on a third-party source: zxing
(https://github.com/zxing/zxing).

Shell command to launch scanner/viewer via wpadebug is:
>adb root
>adb shell

Scanner:
>am start -n w1.fi.wpadebug/w1.fi.wpadebug.QrCodeScannerActivity
Viewer:
>am start -n w1.fi.wpadebug/w1.fi.wpadebug.QrCodeDisplayActivity

QR code string input/output file would be generated in
'/sdcard/wpadebug_qrdata.txt' in the device.

Signed-off-by: Jouni Malinen <jouni@codeaurora.org>