v2.2.0: Power via barrel jack, not via VCC and GND

If the ALog v2.2.0 is powered via th barrel jack (what it's there for!), it uses **15 uA** in sleep mode. If it is powered from VCC and GND on the screw terminals, these connect to the FTDI chip and increase th current draw to **125-130 uA**.

Bottom line: just use the plug.