Document or deprecate and hide Row.show

[schveiguy]

There is an undocumented but public function in Row called show. If it is intended only for debugging, it should be switched to package or private. If it is intended for public consumption it should be documented.

[Abscissa]

This is another one of the things that predates my involvement. Not sure offhand if it's from Steve Teale's, but its definitely been in there ages.

I'd say it should definitely be changed to private (definitely looks more debugging to me and not ideal for public). But that's technically a breaking change so it should coincide with one of our bigger semver version bumps.