render beach from z9
Change POIs displayed at z15 and z16 as discussed on #689

makes #70 less severe or maybe even fixed
follow CartoCSS Style Guidelines
"Always specify zoom levels as either >= or < . Don't use = or =< or >"
render beach from z10
Create new multi-line shields

This expands the shield generation script to cover multi-line shields,
and commits those shields. It doesn't yet use them.
Split concurrent refs into a multi-line shield

This new SQL takes the refs for a way, splits them on ;, and rejoins
them with newlines. When doing this it also calculates the number of lines
and the length of the longest line.

Fixes #670 as best as possible pre-Mapnik 3.
Also fixes #701
Merge branch 'master' into multiline_split_refs
Increase text-dy for default shop style
explain workflow in contribution guidelines
metatile alignments
Delete allotments_3-1.png
rebase allotments.png and remove comment from mss
Merge branch 'allotment-metatile' of github.com:polarbearing/openstreetmap-carto into allotment-metatile
Drop landuse=grave_yard

We still render landuse=cemetery and amenity=grave_yard.

See issue #204.
Drop polygon-opacity from landcover

Drop polygon-opacity from landcover tags that still had it, i.e.:
* tourism = camp_site
* tourism = caravan_site
* tourism = picnic_site
* landuse = garages
* landuse = fill
* leisure = park
* leisure = recreation_ground
* landuse = brownfield
* landuse = landfill
* landuse = construction
* aeroway = aerodome

Polygon-opacity should be avoided, as it gives smudgy and sometimes unexpected
colours in case of overlapping polygons.

Also colour landuse=field as landuse=farm_land, as the old landuse=field
without opacity is too dark.
Merge pull request #768 from polarbearing/workflow-contributions

explain workflow in contribution guidelines
Merge pull request #767 from vholten/shop_names

Increase text-dy for default shop style
Merge pull request #793 from math1985/graveyard

Drop landuse=grave_yard
Move control over road rendering order to SQL

Currently, rendering order of road rendering within one layer is handled
by the z_order column, which comes from osm2pgsql. As such, we have
little control over road rendering without reloading the database.
This PR moves control over the rendering order to the SQL query.

This adds complexity to the SQL queries, but increases customizability,
and simplifies the roads.mms code.

This solves the following issues:

* #462 (Move rendering order road types from osm2pgsql to our SQL queries)
* #163 (Railways are now drawn above roads)
* #167 (Tramway layering issues)
* #168 (Paths are now drawn below link roads)
* Trac 2024 (Service roads are now rendered below link roads)
* Trac 3649 (Service roads are now rendered below race tracks)
* Pedestrian and living streets are now consistently ordered
* Footways are now always displayed under service ways
Correct rendering lowzoom and names of links

This corrects a mismatch between the queries and the style sheet for
the roads-low-zoom and roads-text-name layers.
This should not have influence on performance.