allow stock location state translation

Fixes #4823
add missing admin products submenu translations

this does not change nothing on en locale (tab() helper has fallback values) but it's good as reference for other locales. Makes sense?

Fixes #4284
Eager load all things for api/product/:id

Need to call `reload` on @product at update action so that it loads new
variants and show them properly on the template

Fixes #4287
Fixes #4285
bump jquery-rails and jquery-ui-rails versions
Downcase promotion code comparisons in PromotionHandler::Coupon

Fixes #4211