Add regions Scotland & Northern ireland

[yrro]

The UK is divided into four countries: England (ISO 3166-2 GB-ENG), Wales (GB-WLS), Scotland (GB-SCT) and Northern Ireland (GB-NIR; actually ISO 3166-2 describes GB-NIR as a province not a country... it doesn't matter for the purposes of holiday data).

England and Wales have the same set of public holidays, currently represented by the en-GB locale. But Scotland and Northern Ireland have different sets.

The data set currently doesn't have any subdivisions below the level of an ISO 3166-1 country. So it's not clear how to extend the dataset to incorporate public holidays in Scotland or Northern Ireland.

[lauft]

England, Wales, Scotland, and Northern Ireland should be modeled as regions ENG, WLS, SCT, and NIR in the locale. The holidays then have to be assigned to the specific regions.