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.

Add languages supported by either all default general engines or 10 engines.

Also, fix fetch_languages.py so it can run on python3.

closes issue #863

that support them.
users can still query lesser supported through the :lang_code bang.

utils/fetch_languages.py gets languages supported by each engine and
generates engines_languages.json with each engine's supported language.