Reduce differences between official OpenMapTiles tiles and Tilemaker …

…implementation (#686)

* Add missing features classes to landcover layer.

They are already documented but have been missing in the implementation.

* Add missing place values, add islands mapped as polygons

* Hand over variables to the function instead of relying on global access

* Set correct minzoom for railway features, add railway subclass

Minzoom for railway features depends on railway=*, service=* and
usage=*. Only railway features with specific railway=* values are added
to the vector tiles. This means, railway=construction/disused/… and
railway=fancy_value are ignored.

The OpenMapTiles schema defines a subclass field for railways as well.
This commit adds this field.

* Drop railway features without names from transportation_name

It makes vector tiles smaller if we do not add railway features without
names to the vector tiles.

* Cleanup transportation_name, drop roads without name or ref from it

* Drop layers transportation_name_mid and transportation_name_detail, use
  MinZoom() instead.
* Do not write roads without names or ref into the vector tiles.

* Use write_to_transportation_layer function for ferries

* Do not write ferries without names to the vector tiles

* transportation* layers: minzoom, construction, raceway

* Set correct minzoom values for all roads in the transportation and
  transportation_name layer.
* Add highway=raceway
* Align handling of roads under construction to OpenMapTiles.

* Do not set mtb_scale if the tag is not present

* Add aerialways

* Do not set expressway if the tag is missing

* Add areas for pedestrians, add platforms

* Add missing subclass attribute to transportation layer

* Improve handling of polygons on transporation layer

* Do not write polygons other than infrastructure for pedestrians and
  piers.
* Set minzoom according to area size and absolute minzoom.

* Add man_made=bridge, add brunnel attribute for polygons

* Add man_made=bridge to layer transportation.
* Set brunnel attribute for all polygon features on that layer.

resources/config-openmaptiles.json

@@ -13,8 +13,6 @@
 
 		"transportation":             { "minzoom": 4,  "maxzoom": 14, "simplify_below": 13, "simplify_level": 0.0003 },
 		"transportation_name":        { "minzoom": 8,  "maxzoom": 14 },
-		"transportation_name_mid":    { "minzoom": 12, "maxzoom": 14, "write_to": "transportation_name" },
-		"transportation_name_detail": { "minzoom": 14, "maxzoom": 14, "write_to": "transportation_name" },
 
 		"building":          { "minzoom": 13, "maxzoom": 14 },