nid/pref cookies are also removed

Update OpenSearch Description

btdigg engine: fix text mojibake.

Don't throw away the request if pageno is wrong

Update settings.yml

fix: update buildout

This fix the test failures related to 01d2fb9f703fee2a28cdb4c6583158054f9d7558

[fix] broken link in README from #314

The format changed in 1fcf066, but the link wasn't updated -- until now.

[enh] fix content fetching, parse published date from description for startpage and ixquick

Several changes has been made:
 - Parallel result merge
 - Scoring algorithm slightly changed (see result_score())
 - Proper Thread locking on global data manipulation

TODO check other engines too

Translated Hebrew

Correct the loop through search engines in Pix-Art