Parametric Rocket Fin Alignment Jig

This is a remix of justblair's awesome fin alignment jig. The original had a few minor problems which I've fixed (most of these affected larger jigs in particular):
- fin width is now calculated correctly (it was previously half a tube diameter off)
- the fin tab ends now respect the wall thickness setting
- the brim width is now configurable
- the cylinder smoothness variables have been modified from the $fn method to the $fs/$fa method
- the center cutout is now properly based on the jig height

Aside from the scad file so you can create your own jigs, there's STL files for several common rockets:
- Estes Jetliner
- Estes Curvilinear
- Estes Mosquito
- Estes Mini Der Red Max
- Estes Der Red Max
- Quest Navajo AGM
- Madcow Formula 75

The Estes Jetliner jig is special, it has one fin removed and an added support for the wing. Align the bottom of the jig with the bottom of t