Provide facility for translating strings in code, not just in HTML

All done, thank heavens!

Ha! Got it! https://github.com/folio-org/stripes-core/commit/75076a3e42c0a958c3e12077f244988d422cf0d7

(But I won't close this until I've tidied that code up a bit.)

It's apparent from the source of <IntlProvider> that it creates the intl object itself – see https://github.com/yahoo/react-intl/blob/master/src/components/provider.js – so there's no way to create it outside of React and pass it into <IntlProvider>.

That would have been the sane approach; but in the absence of that, the only way to furnish the intl object to Stripes components (without requiring them to pluck it out of the context themselves as ui-users current does) is to have a component down inside <Root> pull it out of the context, make a new Stripes object that contains it, and arrange for that to be passed down to the lower-level components.

The problem is this: the intl object is furnished only inside the React component <IntlProvider> (which of course exists for precisely that purpose). But by the time we call that component inside <Root>, we've already created the Stripes object. I have made some attempts to have a lower-level React component modify the Stripes object that's established in the surrounding closure, but that is not working for reasons that are not clear to me.

This is proving extremely intractable.

I have code now in ui-users that translates a string outside the context of React: https://github.com/folio-org/ui-users/commit/7aab1368f22ce116a5b4b2c0c1370cf183b6c04b

But it's rather verbose:

What I want to be able to do is just:

but it's hard to get the intl object into the Stripes object.