Currently mapping landuse=farmland in most location results in worse and less readable map for Default map style. Due to massive size it is frequently the most noticeable (or at least one of the most noticeable) features - frequently more prominent than villages or towns. Fixes problem of residential, industrial, farmyard and other landuses not visible enough in sea of landuse=farmland.

distance to landcover closest in color, delta_e94 metric:

hospital/educational area: 4.85
foreground of @bare_ground: 5.02
natural=sand: 5.23
unmapped land: 5.8

closes #1691

update preview image

This saves 4 out 20 seconds on ever Carto-run on my system, and was a bug
anyway.

This improves #1941. Carto processing is now overall about 20% faster on my system.

correct variable name for path/footway tunnel handling

…ry subdivisions only for the biggest countries on z4

This helps significantly with the use of appropriate partial indexes

This avoids getting it wrong in cases of highly-concave regions.

Make residential and tertiary slightly narrower on z13

…carto

Conflicts:
	project.mml

…tmap-carto

Add additional SQL condition for very low admin logic

…liases

rework admin boundaries and admin labels on lower zooms

new farmland color - makes farmland less prominent