On Postgresql versions 11+ add an index to speed up the lookup
of housenumbers for terms found in search_name. This is really
just a band-aid around the query planer's interpretation of the
query.
Also switches to jinja-based preprocessing, which allows to
simplify the SQL files. Use 'if not exists' where possible
so that the step can be rerun to fix missing indexes.
Replaces various hand-crafted replacements of varying format with
a single Jinja2 templating mechanism. Allows full access to
configuration if necessary.
