Switch from digital to analog read for screen photodiode
Switch from digital to analog read for screen photodiode

With the amplified photodiode for screen. The amplification was selected to
never reach saturation but this also means values below digital 1 for even the
brightest screens. Switched to watching the photodiode reading via analogRead.

We also need to add a way to measure and send out screen brightness as a
function of time during transition. Most screens take several milliseconds to
transition and we want to know the shape of this curve as seen by the
photodiode.

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