Displaying the current tool number {after T0/T1/T2/...) on the screen would be helpful with MMU2 or other toolchanger.
The number can be displayed inside the nozzle picture.

In order for interrupt-based wake-ups (as introduced by #1142) to work concurrently with time.Sleep, we need to make some per-board changes.

Previously, sleepTicks (the function used as an interface between the scheduler and the hardware timer) was defined to block until the timer completed, since there was nothing else to do. Now we need to change this so that it bails out when an interrup