Decoupled I18n\View\Helper\AbstractTranslatorHelper from ext\intl
Merge branch 'hotfix/4379'

Close #4379
Fixes #4175
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' into develop

Forward port #4380