Add annotations

Also how to do radio buttons (option-groups) in UI
typo, docs
starting to add rack module
??
cleaning up merge
rack integration and metric attempt

but:
- Not sure scales are correct for each unit type. See annotations.
- Rack needs to have involute teeth on a circle of infinite radius.
factored out Rack gears
format change to unify spaces and

tabs and use standard 4 space tabs
document scale factor and cp/metric start

refactoring (gears not yet split out)
holes became spokes
asin fix (partly)
base function to calc gear fundamentals but results not currently being
used.
fix function to calc base values

tried to insert base calc function - scale errors - commented out
Merge pull request #4 from Neon22/master

Thank you! Great work!