Fixed SQL and mapping bugs.

layers/poi/class.sql

@@ -57,6 +57,7 @@ SELECT CASE class
            WHEN 'water_tower' then 900
            WHEN 'communications_tower' then 900
            WHEN 'wind_turbine' then 900
+           WHEN 'shelter' then 3000
            ELSE 1000
            END;
 $$ LANGUAGE SQL IMMUTABLE

layers/poi/poi.yaml

@@ -134,7 +134,7 @@ layer:
           __AND__:
             subclass: ['generator']
             subtype: ['wind']
-            mapping_key: 'aerialway'
+            mapping_key: ['power']
         communications_tower:
           subclass: ['communications_tower']
         water_tower: