Switch to NE for country labels

[nvkelso]

The NE tables for country ISO and country TLC contain all the information needed to add "country" labels to the map, without a SPAM and abuse vector from OSM.

To switch we'd need to form label geometries from the label_x and label_y columns, and to wire up FCLASS POV (replacing place:XX).

We'd also need to setup remapping of the FCLASS_ISO, FCLASS_TLC, and other FCLASS_* values to valid Tilezen kinds.

See also:

• https://github.com/nvkelso/natural-earth-vector/blob/master/CHANGELOG#L22-L46

Values:

• Admin-0 country (eg United States)
  • kind = country
  • kind_detail = country
• Admin-0 dependency (eg Puerto Rico)
  • kind = country
  • kind_detail = dependency
• Admin-1 region (eg England in United Kingdom)
  • kind = unrecognized
  • kind_detail = macroregion
• Admin-1 states provinces (eg Martinique in France or Alaska in USA)
  • kind = unrecognized
  • kind_detail = region
• Admin-0 lease (eg Baykonur leased to Russia)
  • kind = unrecognized
  • kind_detail = lease
• Admin-0 breakaway and disputed (eg Golan Heights)
  • kind = unrecognized
  • kind_detail = breakaway_disputed
• Admin-0 claim area (eg Crimea)
  • kind = unrecognized
  • kind_detail = claim_area
• Admin-0 indeterminant (eg Spratly Islands)
  • kind = unrecognized
  • kind_detail = indeterminant
• Island group (eg Midway Islands part of US Minor Outlying Islands dependency)
  • kind = unrecognized
  • kind_detail = island_group
• Island (eg Antigua a component of Antigua and Barbuda country)
  • kind = unrecognized
  • kind_detail = island

Originally posted by @nvkelso in #2069 (review)