Cleaned up more code from landmark that wasn't used. Experimenting with power generator:source stuff

layers/poi/layer.sql

@@ -34,7 +34,7 @@ SELECT osm_id_hash                                  AS osm_id,
                THEN NULLIF(religion, '')
            WHEN subclass = 'pitch'
                THEN NULLIF(sport, '')
-           when class = 'power'
+           when power = 'generator'
                THEN NULLIF(source, '')
            ELSE subclass
            END                                      AS subclass,

layers/poi/mapping.yaml

@@ -376,6 +376,9 @@ def_poi_fields: &poi_fields
   - name: sport
     key: sport
     type: string
+  - name: power
+    key: power
+    type: string
   - name: source
     key: "generator:source"
     type: string