document what's required to make the 12V switcher on v2.0 work

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+2018.05.30
+
+To make v2.0 useful:
+
+Replace the 27k in the lower leg of the AP3012 comparator circuit with a 56k
+to drop the voltage from ~27V to just under 12V.
+
+In the AP3012 circuit, rotate the inductor and 4.7uF caps 90 degrees, and lift
+pin 5 of the IC, to detach all of them from the 3.3V rail.  Use a wire to 
+connect all of them to pin 4, the gpio driving the circuit.
+
+The net effect is that we're making 12V from the gpio, which means all the LED
+current and switcher inefficiency is coming as current through that gpio.  The
+measured LED current is around 7mA, so this is "safe" for the SOC, but really
+not a great plan... 
+
+Need to redesign this in the future to use a transistor/FET switch.