Define DestroyWithOrdersError within user_class_extensions

This is needed in Admin::UsersController, but only for custom user classes that didn't previously implement this class

Fixes #4453
fix open transition on adjustments

Fixes #4444
Include localization files for select2 in admin backend

Fixes spree/spree_i18n#362
Show a good error message when stock location creation is attempted without a valid default country existing

Fixes #4272