Update README to reflect changes in generator

The generator inserts lines into different files now:

https://github.com/spree/spree_i18n/blob/master/lib/generators/spree_i18n/install/install_generator.rb

Fixes #378
renamed and updated UA/UK locale

I've made this pull request to replace [#358](https://github.com/spree/spree_i18n/pull/358), which doesn't merge cleanly.

Fixes #379
Update ru.yml definition of subtotal

There are two different ways to translate "subtotal" into Russian. We need to use one of them, not both two: "Подитог" (proposed) xor "Подытог".
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В 2х случаях употребляется "Подитог", в одном - "Подытог".
Нужно определиться, как переводить. Предлагается вариант "Подитог".

Fixes #382
Fix failing option_type spec

Conflicts:
	spec/features/admin/translations_spec.rb
[de] Add missing admin tab translations for option types, properties and prototypes
added es-EC locale (just a copy of 'es')

Fixes #388