rerank results by query

The algorithm is similar to the PHP reranking and uses the terms from
the display name to check against the query terms. However instead of
exact matching it uses a per-word-edit-distance, so that it is less
strict when it comes to mismatching accents or other one letter
differences.

Country names get a higher penalty because they don't receive a
penalty during token matching right now.

This will work badly with the legacy tokenizer. Given that it is
marked for removal, it is simply not worth optimising for it.

nominatim/api/search/query_analyzer_factory.py

@@ -30,6 +30,15 @@ class AbstractQueryAnalyzer(ABC):
         """
 
 
+    @abstractmethod
+    def normalize_text(self, text: str) -> str:
+        """ Bring the given text into a normalized form. That is the
+            standardized form search will work with. All information removed
+            at this stage is inevitably lost.
+        """
+
+
+
 async def make_query_analyzer(conn: SearchConnection) -> AbstractQueryAnalyzer:
     """ Create a query analyzer for the tokenizer used by the database.
     """