[fix] decoding of saved preferences in the URL

To compress saved preferences in the URL was introduced in 5f758b2d and
slightly fixed in 8f440146.  But the main fail was not fixed; The decompress
function returns a binary string and this binary should first be decoded to a
string before it is passed to urllib.parse_qs.

BTW: revert the hot-fix from 59734917

Related-to: https://github.com/searxng/searxng/issues/166


Signed-off-by: Markus Heiser <markus.heiser@darmarit.de>