Screen: Hygrometer and Thermometer monitoring

Currently there's a thermistor provided by the fan control (see #1339). Translating the measurements of this device to voltage is configurable via the 3 buttons and LED on the fan control board.

The problem is that this doesn't address thermal runaway or any related problem since the best it can do is set the fans to 24v.

Instead, a better design, would be to get temperature (and if easy, moisture) readings from, say, an I2C/SPI connected device to the microcontroller and then be able to (in order of LOE/importance)

[ ] reduce screen brightness
[ ] shut off critical system components
[ ] control the fan voltage

For the last one, it's really up to the idea of whether we are ditching the current dc-dc boost/motor controller (#1339).

Also, given the humidity of socal, it's hard to know what the right response is to the right hygrometer level reading. We need to find that out.

WaiveCar / Waivecar

Screen: Hygrometer and Thermometer monitoring #1341