implement translation behavior default locale

Unless explicitly overriden, the behavior now reads I18n::defaultLocale() to find the locale to return translations in.

Bundled with this change set is adding support to the translate behavior
for unhydrated result sets

Closes #4509

Ref #4660 
> My site's locale is en_us

What language is your content by default, and what is the value of `intl.default_locale` in php.ini?