Add missing Dutch emoji translations (#1682)

I noticed the Dutch emoji file was missing some translations. I cleaned
the whole file where I could:

- added missing translations
- longhand numbers
- fixed translation for ⚒ emoji
- removed all capital letters from translations
- removed colons and commas from translations
- removed the "flag" prefix from all county flags for consistency with
the English emoji file
- split abbreviations like OK in separate letters

Feedback welcome.