Added missing key_field to the aerodrome_label & mountain_peak def (#686)

aerodrome_label & mountain_peak queries return `osm_id`, but they
are not declared in the data source.  I think we should either remove
the `osm_id` from the query result, or declare the data source.

layers/aerodrome_label/aerodrome_label.yaml

@@ -27,6 +27,8 @@ layer:
     ele_ft: Elevation (`ele`) in feets.
   datasource:
     geometry_field: geometry
+    key_field: osm_id
+    key_field_as_attribute: no
     srid: 900913
     query: (SELECT osm_id, geometry, name, name_en, name_de, {name_languages}, class, iata, icao, ele, ele_ft FROM layer_aerodrome_label (!bbox!, z(!scale_denominator!), !pixel_width!)) AS t
 schema:

layers/mountain_peak/mountain_peak.yaml

@@ -19,6 +19,8 @@ layer:
     rank: Rank of the peak within one tile (starting at 1 that is the most important peak).
   datasource:
     geometry_field: geometry
+    key_field: osm_id
+    key_field_as_attribute: no
     srid: 900913
     query: (SELECT osm_id, geometry, name, name_en, name_de, {name_languages}, class, ele, ele_ft, rank FROM layer_mountain_peak(!bbox!, z(!scale_denominator!), !pixel_width!)) AS t
 schema: