**This is a pull-request against the lua branch**

This PR proposes a database-reload. It changes the documentation on the use of
osm2pgsql, and adds a .lua file for preprocessing.

This database import aims to be backwards compatible with older versions of
the style.

This resolves (at least part of) #1504.

 #Hstore
Adding the hstore option to osm2pgsql allows the database to use all keys.

This PR proposes using hstore for new keys, and using traditional columns for
old keys. This allows us to stay compatible with old versions of the style.

According to [@pnorman's benchmarks](http://www.paulnorman.ca/blog/2014/03/osm2pgsql-and-hstore/),
using hstore without dropping columns would lead to a 9% size increase and a
0.38% speed decrease. Given the benefits of having all columns available, I
would consider this acceptable.

 # Make polygon/linestring decision based on value
This is based on the following unmerged PR to osm2pgsql:
osm2pgsql-dev/osm2pgsql#346

It makes the polygon/linestring decision based on the tag value, in addition to
the tag key. In particular, highway=services and junction=yes are now treated as
polygon, while leisure=track, man_made=embankment, man_made=breakwater,
man_made=groyne, natural=cliff, natural=tree_row, historic=citywalls,
waterway=derelict_canal, waterway=ditch, waterway=drain, waterway=river,
waterway=stream, waterway=wadi, waterway=weir, power=line, and power=minor_line
are now treated as linestring.

This resolves #1362, resolves #137, resolves #268, and resolves #892.

 # Rendering order
The new .lua file creates a osmcarto_z_order value in the database, which stores
the rendering order we use. This will allow us to simplify the road queries.

 # Recommend -G flag for multipolygons
This resolves #59.

 # Import ele on buildings
This resolves #101.

 # Delete more meta-tags from imports
The .lua file drops some more meta-information from imports that is of no
need for rendering.

This is based on the following unmerged PR to osm2pgsql:
* osm2pgsql-dev/osm2pgsql#532

…ua file

…ua_changes

* Convert layer to integer and use it in queries
* Use layer instead of z_order in queries where possible

… into lua_changes

…p-carto into lua_changes

Conflicts:
	openstreetmap-carto.style
	project.mml

Use 4sp for Lua indents

Tag v2.41.0

Conflicts:
	project.mml

Tag 2.42.0

Conflicts:
	project.mml

Sport is a non-physical key, so it should always be combined with
another, physical key. That physical key should define whether the
object is a polygon or line. Since an object with a polygon key
and a line key will be treated as polygon, treating sport as line
by default is the sane default.

For example:
* sport=running, highway=footway should be treated as line. The
  current PR accomplishes this, before it would be a polygon.
* sport=soccer, leisure=pitch should be treated as polygon. Nothing
  changes here.

This resolves ... #854 but only after it gets merged into master.

Drop sport from polygon_keys

Tag v2.43.0

Conflicts:
	project.mml
	project.yaml

Tag v2.44.0

Conflicts:
	project.mml

Tag v2.44.1

Conflicts:
	project.mml

Use correct location for Lua script

Resolves #2277, resolves #2258

Treat leisure=slipway, natural=ridge,arete as linestring by default

Tag v2.45.0

Add documentation about needing hstore

Lua rail roads

Consider building:part a polygon tag

Tag v3.0.0

This code takes a stricter view on what a multipolygon is, and adds
test coverage for relation handling.

Rewrite relation handling code

Tag v3.0.1

Add SQL style notes on hstore

Tag v3.1.0

Remove support for old-style multipolygons

Tag v3.2.0