Add code to turn on/off the LED

[codedance]

Suggested from Mark T. Add code to turn on/off the LED. Would be good edition to the command set. i.e. warn before you're shot or powered up when it's active.

Code suggestion below. Will do this soon.

def led(cmd):

DEVICE.ctrl_transfer(0x21, 0x09, 0, 0, [0x03, cmd, 0x00,0x00,0x00,0x00,0x00,0x00])

…

elif command == "led":

    if value == 0:

        led(0x00)

    else:

        led(0x01)