Ported functions for the import of special phrases from php to python.

- the command is now --import-special-phrases
- the output is not an sql file anymore, data are directly imported to the database.
- the little part on the documentation (section data import) has been modified.

nominatim/clicmd/__init__.py

@@ -10,3 +10,4 @@ from .refresh import UpdateRefresh
 from .admin import AdminFuncs
 from .freeze import SetupFreeze
 from .transition import AdminTransition
+from .special_phrases import ImportSpecialPhrases