Function screw_to_axis 

pub fn screw_to_axis<T: Float>(q: &V3<T>, s: &V3<T>, h: T) -> V6<T>

Takes a parametric description of a screw axis and converts it to a normalized screw axis

Function arguments: q: V3 a point lying on the screw axis s: V3 a unit vector in the direction of the screw axis h: Float The pitch of the screw axis

Output: V6 A normalized screw axis described by the inputs