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/aeroway/aeroway.yaml

@@ -24,7 +24,7 @@ layer:
     geometry_field: geometry
     query: (SELECT geometry, ref, class FROM layer_aeroway(!bbox!, z(!scale_denominator!))) AS t
 schema:
-  - ./layer.sql
+  - ./aeroway.sql
 datasources:
   - type: imposm3
     mapping_file: ./mapping.yaml