Proof of concept relative time message customization

Just a quick attempt to allow message costumization. It preserves the existing strings so you can see what was supposed to be there. Passing in a new catalog or overriding through extending the ones you want to customize would let you change the behavior.

Doesn't really attempt to solve plurals or i18n or different language positions of numerals in relation to text. That would require using an an actual i18n approach with templates and parameters.