timerIsr tick reduced more, divisble with line freq

Changed timerIsr tick to be evenly divisible with line frequency of 50Hz
or 60Hz. This further reduces the tick rate from 4KHz to 1666Hz.

At this frequency, UI is a lot more responsive. Knob polling has been
changed to every timerIsr firing (with slight code size reduction).
ClickEncoder is modified slightly to allow adjusting values based on
this new tickrate, and these values are in this main source file.

Changed process run screen update to update the screen more smoothly
with these settings. Setpoint changes smoothly, no more jumping around.

DEFAULT_LOOP_DELAY was fucked last time, I think. Now it is now
calculated from the cycle time automatically.