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
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
Refactor waterway bridges

* Rivers, streams, ditches and drains are now also rendered on bridges.
  This resolves https://trac.openstreetmap.org/ticket/3005.
* Canals on bridges now have a width consistent with canals not on bridges.
Make minimum landuse zoom levels more consistent

The minimum zoom levels are currently rather inconsistent. For example meadow
and farmland have a different minimum zoom level. This PR aims to improve this.

This PR lets all major landuse start at z10 (like most do already), except for
wood / forest. Smaller objects will start at z13.

Concrete changes in minimum zoom levels:

* tourism=camp_site, tourism=caravan_site, tourism_picnic_site from z13 to z10
* landuse=quarry from z11 to z10
* landuse=garages from z12 to z13
* landuse=farmyard, landuse=farm, landuse=farmland from z9 to 10
* landuse=village_green from z11 to z10
* natural=desert from z8 to z10 (solves partially #773)
* aeroway=apron, aeroway=aerodrome from z12 to z10
* highway=services, highway=rest_area from z14 to z10
Render names on junctions

This renders names of junction=yes and junction=roundabout.
Rendering is similar to highway=motorway_junction.
Change junction rendering

* Also render name for traffic_signals without junction tag
* Don't render junction names on roundabouts
* Render junctions in black and in a smaller font
* Offset junction names only when the traffic signal icon shows
* Start rendering junctions from z14
* Wrap lines
Re-add special rendering of construction links

This resolves #909.
Order POI by way_area

POI are now ordered by way area. Note that icons are never rendered on top
of each other, so this has only influence on priority decision of icon
rendering.

Large POI (such as universities, malls, etc.) are now rendered with higher
priority.

The old order was:
* Render points with higher priority than areas
* Icon priority from high to low: tourism, amenity, highway, waterway,
  man_made, historic, shop, leisure
* Text priority from high to low: place, amenity, natural, historic, leisure,
  landuse, tourism, waterway, man_made, shop, aeroway
It is clear that the old order was quite a mess.

* Resolves partially #287
* Resolves partially #797
* Resolves #802
* Resolves https://trac.openstreetmap.org/ticket/4100
Prevent combinatorial explosion
Various corrections to 'Order POI by way_area' PR
Solve combinatorial explosion caused by shop != ''