Add a special index that contains the place nodes buffered by their
respective area according to their search rank. This replaces the
maximum area search for place nodes and reduces drastically the number
of place nodes that need to be retrieved.
If no parent can be found for an interpolation, there is most
likely a data error involved. So don' t show these interpolations
in reverse search results.
The fairly complex where condition of idx_placex_geometry_placenode
won't always be matched by the query planner if the condition
part doesn't appear verbatim in the query.
Fixes#2480.
Always look up the closest housenumber before looking up
interpolations. This ensures that closer housenumbers are
preferred over interpolations.
Fixes#2214.