Need home-position hole in spool gear

[scottbez1]

In order to detect the home position for closed-loop control, need to cut a hole/slot into the spool gear for the GP2S60 reflectance sensor to detect. This has worked well empirically with a hand-drilled hole (had to use a permanent black marker to color the inside), so just need to add it to the 3d model at the right location. A rough initial guess was accidentally committed with c2433e2, but the position should be double-checked against the finalized pcb layout.