unify ICUNameProcessorRules and ICURuleLoader

There is no need for the additional layer of indirection that
the ICUNameProcessorRules class adds. The ICURuleLoader can
fill the database properties directly.

test/python/test_tools_check_database.py

@@ -53,7 +53,7 @@ def test_check_tokenizer(temp_db_conn, def_config, monkeypatch,
                          check_result, state):
     class _TestTokenizer:
         @staticmethod
-        def check_database():
+        def check_database(_):
             return check_result
 
     monkeypatch.setattr(chkdb.tokenizer_factory, 'get_tokenizer_for_db',