Add Latvian (lv) flavor with Latvian municipalities

110 municipalities and 9 republican cities.

Translations will come later.
Add Latvian (lv) postal code field (LV-XXXX)
Add Latvian (lv) personal code field (XXXXXX-XXXXX)
Merge pull request #68 from intgr/lv

Add Latvian (lv) flavor: postal code, personal code and municipality fields