Backport Ukrainian translation from master

`master` branch doesn't delete any strings in comparison with `2-3-stable`, only adds new ones, so I just copied this file from `master`, not bothering to delete those new strings, as they won't interfere with existings. There are only 4 potentially incompatible strings:
```
$ git diff master 2-3-stable core/config/locales/en.yml | grep ^\+
+++ b/core/config/locales/en.yml
+        subtotal: ! 'Subtotal: %{subtotal}'
+        total: ! 'Order Total: %{total}'
+        subtotal: ! 'Subtotal: %{subtotal}'
+        total: ! 'Order Total: %{total}'
```
(the diff is from spree/spree)

In spree's `master` they are without parameters. But it turns out I wrongly left them so in my Ukrainian file in spree_i18n's `master`. So they should fit to `2-3-stable`, but have to be updated in `master`, which I'll do next.