Add gridrank attribute

layers/poi/class.sql

@@ -1,3 +1,33 @@
+CREATE OR REPLACE FUNCTION poi_class_rank(class TEXT)
+RETURNS INT AS $$
+    SELECT CASE class
+        WHEN 'hospital' THEN 20
+        WHEN 'park' THEN 25
+        WHEN 'cemetery' THEN 30
+        WHEN 'bus' THEN 50
+        WHEN 'attraction' THEN 70
+        WHEN 'harbor' THEN 75
+        WHEN 'college' THEN 80
+        WHEN 'school' THEN 85
+        WHEN 'stadium' THEN 90
+        WHEN 'zoo' THEN 95
+        WHEN 'town_hall' THEN 100
+        WHEN 'campsite' THEN 110
+        WHEN 'cemetery' THEN 115
+        WHEN 'park' THEN 120
+        WHEN 'library' THEN 130
+        WHEN 'police' THEN 135
+        WHEN 'post' THEN 140
+        WHEN 'golf' THEN 150
+        WHEN 'shop' THEN 400
+        WHEN 'grocery' THEN 500
+        WHEN 'fast_food' THEN 600
+        WHEN 'clothing_store' THEN 700
+        WHEN 'bar' THEN 800
+        ELSE 1000
+    END;
+$$ LANGUAGE SQL IMMUTABLE;
+
 CREATE OR REPLACE FUNCTION poi_class(subclass TEXT)
 RETURNS TEXT AS $$
     SELECT CASE