enable BDD tests for different tokenizers

The tokenizer to be used can be choosen with -DTOKENIZER.

Adapt all tests, so that they work with legacy_icu tokenizer.
Move lookup in word table to a function in the tokenizer.
Special phrases are temporarily imported from the wiki until
we have an implementation that can import from file. TIGER
tests do not work yet.

test/bdd/environment.py

@@ -20,6 +20,7 @@ userconfig = {
     'API_TEST_DB' : 'test_api_nominatim',
     'API_TEST_FILE'  : (TEST_BASE_DIR / 'testdb' / 'apidb-test-data.pbf').resolve(),
     'SERVER_MODULE_PATH' : None,
+    'TOKENIZER' : None, # Test with a custom tokenizer
     'PHPCOV' : False, # set to output directory to enable code coverage
 }