Gravity sucks (new counter-weight)

[spacekookie]

https://github.com/Libreflip/control/blob/323162a08fcbe8baa4697ccff7df78033063b6f3/bookscanner_control/bookscanner.cpp#L71

This is not going to be true anymore very soon!

[ij0n]

Because of the counterweight, the suction box can't "fall down" into its lowest position anymore. It should not change its position, if the motor is switched off.

This means we have to find a new way (software or hardware or both!) to find the lowest position - a position where the suctionbox is gently pressed against the book. Any ideas?