Rename generic layer.sql to actual_layer_name .sql (#1034)

Following layers had generic `layer.sql` name.

- `aerodrome_label`
- `aeroway`
- `housenumber`
- `mountain_peak`
- `park`
- `place`
- `poi`
- `transportation`
- `transportation_name`
- `water_name`

This PR renames `layer.sql` to `aerodrome_label.sql`, `aeroway.sql`...

layers/mountain_peak/mountain_peak.sql

@@ -0,0 +1,62 @@
+-- etldoc: layer_mountain_peak[shape=record fillcolor=lightpink,
+-- etldoc:     style="rounded,filled", label="layer_mountain_peak | <z7_> z7+" ] ;
+
+CREATE OR REPLACE FUNCTION layer_mountain_peak(bbox geometry,
+                                               zoom_level integer,
+                                               pixel_width numeric)
+    RETURNS TABLE
+            (
+                osm_id   bigint,
+                geometry geometry,
+                name     text,
+                name_en  text,
+                name_de  text,
+                class    text,
+                tags     hstore,
+                ele      int,
+                ele_ft   int,
+                "rank"   int
+            )
+AS
+$$
+SELECT
+    -- etldoc: osm_peak_point -> layer_mountain_peak:z7_
+    osm_id,
+    geometry,
+    name,
+    name_en,
+    name_de,
+    tags->'natural' AS class,
+    tags,
+    ele::int,
+    ele_ft::int,
+    rank::int
+FROM (
+         SELECT osm_id,
+                geometry,
+                name,
+                COALESCE(NULLIF(name_en, ''), name) AS name_en,
+                COALESCE(NULLIF(name_de, ''), name, name_en) AS name_de,
+                tags,
+                substring(ele FROM E'^(-?\\d+)(\\D|$)')::int AS ele,
+                round(substring(ele FROM E'^(-?\\d+)(\\D|$)')::int * 3.2808399)::int AS ele_ft,
+                row_number() OVER (
+                    PARTITION BY LabelGrid(geometry, 100 * pixel_width)
+                    ORDER BY (
+                            substring(ele FROM E'^(-?\\d+)(\\D|$)')::int +
+                            (CASE WHEN NULLIF(wikipedia, '') IS NOT NULL THEN 10000 ELSE 0 END) +
+                            (CASE WHEN NULLIF(name, '') IS NOT NULL THEN 10000 ELSE 0 END)
+                        ) DESC
+                    )::int AS "rank"
+         FROM osm_peak_point
+         WHERE geometry && bbox
+           AND ele IS NOT NULL
+           AND ele ~ E'^-?\\d{1,4}(\\D|$)'
+     ) AS ranked_peaks
+WHERE zoom_level >= 7
+  AND (rank <= 5 OR zoom_level >= 14)
+ORDER BY "rank" ASC;
+
+$$ LANGUAGE SQL STABLE
+                PARALLEL SAFE;
+-- TODO: Check if the above can be made STRICT -- i.e. if pixel_width could be NULL