Fixes#1191
This PR suppresses `highway=service` at zoom 12, where it is not a useful level of detail. This makes OpenMapTiles consistent with openstreetmap-carto, which does not begin showing `highway=service` until raster zoom 14 / vector zoom 13.
Additionally, this PR suppresses `highway=service` + `service=parking_aisle` / `service=driveway` from zooms 12-13, as this detail is excessive below zoom 14. As a point of comparison, openstreetmap-carto does not begin showing `service=parking_aisle` / `service=driveway` until raster zoom 16 (vector zoom 15).
This PR adds a layer for `highway=motorway_junction` features.
This implementation of highway exits in the transportation_name layer add to the existing layer table structure, and renames the internal column name from "construction" (which was already overloaded with non-construction usages) to "subclass", which will be less confusing to future developers. The string 'junction' is used as the universal sub-class for highway exits.
A new documentation PR has been opened at openmaptiles/www.openmaptiles.org#69 to reflect these changes in the documentation.
quicker and cleaner diagram image generation.
Remove etl-graph and mapping-graph targets - redundant
Also, the obsolete "fields" is still in Imposm's code and both names are accepted,
but "fields" is not documented anywhere (PR submitted), and could be removed at any moment.
Our docs were not supporting it until this PR, so renaming it at the same time.
Several images have been updated due to a more inclusive mapping scan
Requires https://github.com/openmaptiles/openmaptiles-tools/pull/147 (merged)
