56375826 documentation improvements

I've extracted documentation changes from my bazillion commits in my never-ending "Moby Dick" Billing-Logic branch that conflated documentation, refactoring, and test improvements.

There's one substantive change in this PR... in the very first file below, so easy to find. It just changes the value of Rubygems.

I'm not done with documentation changes, but I couldn't work on my original branch any more because it has become an octopus and has lived way too long, so I'm pulling the commits out into different PRs and then will work from master again after the changes get merged in.