* new formatjs/intl-relativetimeformat and intl-pluralrules dependencies as react-intl polyfills

* changes in jest.config.js, webpack.base.babel.js, i18n.js and ToggleOption component according to react-intl upgrade guide

* various snapshot updates due to internal react-intl changes

Signed-off-by: mhatvan <markus_hatvan@aon.at>

…erplate into chore/upgrade-react-intl-to-v3

* react-intl upgrade from 3.1.9 to 3.3.0

* switch from intl-pluralrules to @formatjs/intl-pluralrules

* update i18n.js and i18n.md

Signed-off-by: mhatvan <markus_hatvan@aon.at>

* change add-locale-data.hbs and intl-locale-data.hbs generation

* add istanbul ignore to conditional polyfill imports

* remove intl polyfill in app/app.js and polyfill-intl-locale.hbs

* change documentation url for intl webpack transpilation

Signed-off-by: mhatvan <markus_hatvan@aon.at>

Signed-off-by: markushatvan <markus_hatvan@aon.at>

…ndows environments

Signed-off-by: markushatvan <markus_hatvan@aon.at>

…erplate into chore/upgrade-react-intl-to-v3

Signed-off-by: mhatvan <markus_hatvan@aon.at>

…eact-boilerplate into chore/upgrade-react-intl-to-v3

…erplate into chore/upgrade-react-intl-to-v3

* add full-icu package to fix locale data missing error in jest tests

* add english locale data polyfill for Intl.Pluralrules and Intl.RelativeTimeFormat

* change language generation to add locale data polyfills after english locale data

Signed-off-by: mhatvan <markus_hatvan@aon.at>

Update react-intl to latest version.  Update LanguageProvider, app.js,
and i18n.js in both app and template as described below.

i18n.js

- Despite the comment at the top of the file, i18n.js is not being used
  by the extract-intl script anymore, and can therefore use import/export
  syntax.

- The translation files are now imported dynamically so that only the
  necessary translations are included. In the example app, this doesn't
  make much difference, but when there are many locales, loading json
  files individually will make a significant difference.

- Create fetchMessages convenience function for importing/formatting
  translations.

app.js

- Update dynamic imports of Intl polyfills to @formatjs/intl-pluralrules
  and @formatjs/intl-relativetimeformat.

- Remove translationMessages as they are now being fetched by the
  getTranslationMessages Saga.

LanguageProvider

- The CHANGE_LOCALE action now triggers the getTranslationMessages Saga.
  The Saga will use the fetchMessages function in i18n.js to fetch the
  appropriate messages file and then update the locale and messages.

- If the messages are unable to be fetched, the saga will fall back to
  the default locale and messages.

generators

- Fix all language generators so that they work properly for new
  i18n.js/app.js implementaiton.

- Previous commit failed because the app.js template was not formatted
properly