R18n support for locale date formats - rebirthing form the ashes

So, @mattr- make some suggestions in the comments of #386. I tried to attend the first one. Here is @mattr- 's suggestions, and a plus.

- [x] Add additional functionality that does nothing if there is no _locale directory. This means that for 99% of the people that don't use this feature, nothing changes for them.
- [ ] Update the site documentation in site on the master branch.
- [ ] Create the tests for the new functionality.

I'm just creating this PR to discuss this things above, and the things that I already done too.