Decoupled I18n\View\Helper\AbstractTranslatorHelper from ext\intl
Merge pull request #4380 from Slamdunk/hotfix/intl-optional

Decouple I18n\View\Helper\AbstractTranslatorHelper from ext\intl
[#4380] CS fixes

- s/Extensions/Extension/g
- Added explanatory comments
- Alias both exception types in DateTime validator
Merge branch 'hotfix/4380'

Close #4380