Herringbone Clockwork Option

Rustedrobot reports that there are alignment problems with the gears from the clockwork library. Some of that can be fixed by making the gears thicker, and tightening the tolerances between the gears and the shafts they sit on... but he points out that herringbone gears might really help.

I implemented herringbone gears in the clockwork library, made sure they meshed, and while I was at it, beefed up the pinions and introduced a little (parametric) space between the two gears of a wheel... be