WIP: Rewrite to use a bezier curve for fan speeds

Results in smoother fan control and significantly simpler logic. On my GPU this currently keeps the fan steady and maintains the temperature at 51 degrees when idle in 4K, and a stable 65 degrees when running at full load. At lower resolutions it will idle the fan still, I believe, but I'll need to check this as the curve is based on a 0% fan speed value at 30 degrees.