Unify code of power=tower and power=pole (gravitystorm#3561)

* unify code of power=tower and power=pole

* invert pole and tower

* add ORDER condition

* fix ORDER BY

Author: jragusa

power.mss

@@ -33,21 +33,20 @@
 }
 
 #power-towers {
-  [zoom >= 14] {
-    marker-file: url('symbols/man_made/power_tower_small.svg');
-    marker-width: 3;
-  }
-  [zoom >= 15] {
-    marker-file: url('symbols/man_made/power_tower.svg');
-    marker-width: 5;
-  }
-  [zoom >= 17] {
-    marker-width: 7;
+  [power = 'tower'] {
+    [zoom >= 14] {
+      marker-file: url('symbols/man_made/power_tower_small.svg');
+      marker-width: 3;
+    }
+    [zoom >= 15] {
+      marker-file: url('symbols/man_made/power_tower.svg');
+      marker-width: 5;
+    }
+    [zoom >= 17] {
+      marker-width: 7;
+    }
   }
-}
-
-#power-poles {
-  [zoom >= 16] {
+  [power = 'pole'][zoom >= 16] {
     marker-file: url('symbols/square.svg');
     marker-fill: #928f8f;
     marker-width: 3;

project.mml

@@ -1707,25 +1707,19 @@ Layer:
       <<: *osm2pgsql
       table: |-
         (SELECT
-            way
-          FROM planet_osm_point
-          WHERE power = 'tower'
+            way,
+            power
+        FROM planet_osm_point
+        WHERE power IN ('tower', 'pole')
+        ORDER BY
+          CASE
+            WHEN power = 'tower' THEN 1
+            WHEN power = 'pole' THEN 2
+            ELSE NULL
+          END
         ) AS power_towers
     properties:
       minzoom: 14
-  - id: power-poles
-    geometry: point
-    <<: *extents
-    Datasource:
-      <<: *osm2pgsql
-      table: |-
-        (SELECT
-            way
-          FROM planet_osm_point
-          WHERE power = 'pole'
-        ) AS power_poles
-    properties:
-      minzoom: 16
   - id: roads-text-ref-low-zoom
     geometry: linestring
     <<: *extents