Add match_language function in utils to match any user given
language code with a list of engine's supported languages.
Also add language_aliases dict on each engine to translate
standard language codes into the custom codes used by the engine.
languages.py can change, so users may query on a language that is not
on the list anymore, even if it is still recognized by a few engines.
also made no and nb the same because they seem to return the same,
though most engines will only support one or the other.
