The 'scrap_img_by_id' function didn't return any longer anything useful. This
fix allows the google images engine to present the full source image instead of
only the thumbnail.
The function scrap_img_by_id() is rpelaced by a fully rewrite to parse image
URLs by a regular expression. The new function parse_urls_img_from_js(dom)
returns a mapping of data-id to image URL.
Closes: https://github.com/searxng/searxng/issues/909
Signed-off-by: Markus Heiser <markus.heiser@darmarit.de>