Translatable route prefixes

| Q             | A
| ------------- | ---
| Bug fix?      | no
| New feature?  | yes
| BC breaks?    | yes (I18nRoute is removed and replace by I18nRouteCollectionBuilder::buildCollection)
| Deprecations? | no
| Tests pass?   | yes
| Fixed tickets | #29
| License       | MIT

This PR adds the option to localize prefixes both using a array or using replacement of {_locale}.

See Tests/Fixtures/import_prefix_locale.yml and Tests/Fixtures/import_prefix_locale.xml for a example.

Sorry but I don't have time to update the README.md