move meta information from comment to the about variable so the preferences, the documentation can show these information
Engine list: ahmia, duckduckgo_images, elasticsearch, google, google_images, google_videos, youtube_api
use from searx.engines.duckduckgo import _fetch_supported_languages, supported_languages_url # NOQA so it is possible to easily remove all unused import using autoflake: autoflake --in-place --recursive --remove-all-unused-imports searx tests
