* statuses: detect slow fan via quadratic regression and halts (hard stops) with constant threshold
* remove unsafe channels' copy and make FanCtrl own the channels
* scale fan values so that they would fit 0.05-1.0 PWM at all times
* rename fan-restore to fcurve-restore
* style, names and docs adjustments
Signed-off-by: Egor Savkin <es@m-labs.hk>