Besside-ng: Added automatic channel detection of 2GHz and 5GHz channels

[moonrk]

The channels in besside-ng were hardcoded from 1 to 11 unless using the -c option to lock to a specific channel.

I've made the necessary changes to detect the channels that the wifi adapter supports automatically, including 5GHz channels. The scanning process will thus be able to scan channels 1-14, 36-64, 100-144, 149-161 and 165 if they are supported.

This also fixes issue #106.

Tested on Alfa AWUS036NHA and Alfa AWUS036AC wifi adapters.

[strasharo]

Awesome, this works, just tested it on AWUS036H. Thanks a lot @moonrk . @Mister-X- , can we have this merged, please? :)

[Mister-X-]

It's nice to have it in bessides-ng but that needs to be global, in osdep, so airodump-ng can query it. And split it in 2 parts, 2.4GHz and 5GHz.

Other tools also need to be able to query which channels are available (to validate them), so a third function to check that in osdep would be useful.