Light guide length (very slightly) improperly calculated from PMT placement position parameter

[cameronc137]

In commit 233c075 there is the addition of a comment.

"the dzRef length computation also needs a dxRef*angle component (in this nomenclature it would be addition) so that the PMT placement in CAD solidworks will work out."

I don't remember exactly the problem, but I know that it has to do with a missing length*sin(small angle) shift, I think coming from the reflector opening angle being > 0 degrees

This issue is mostly to properly track my thoughts from a year ago so it eventually gets addressed.