Migrate date format configuration to CMI

Date format configuration is translatable in a very awkward way. Some of the strange things:

1. The date_format_locale table is defined by system module with the other date format tables.
2. Although the table is named date_format_locale, it stores formats keyed by {language}.langcode (as expected)
3. Locale module includes all kinds of custom code to make this happen, making this a special feature (vs. contact forms or your site name, which are not at all translatable)

This is a relatively self contained, well defined part of Drupal core that would be a great goal for CMI to convert to the new Drupal 8 config system with language support in mind getting locale module rid of this special case implementation. The definite plan for Drupal 8 is that language support is so ubiquitous that modules take care of it instead of trying to rely on an outside entity to solve it all for them. After all the modules know how their data is input (forms, validation, etc) and how and when it is loaded and what kind of language should it be loaded with.

Tagging for CMI, D8MI and language-config under D8MI.