Change polling interval to a regular 1ms

Make use of PMW3360's Angle_Tune register

fixed hysteretic scroll

moved sketch into top-level directory named 'production'

changed scrolling algorithm to be much more robust, using a state machine instead of state-free processing

Update README.md

added electricals and mechanicals

Rev A 3D printed parts.

R1.003 schematics in PDF form and Gerbers for sending to a PCB house.

R1.003 electronics design files.