Avoid UnicodeEncodeError when redirecting standalone output

This modification allows us to deactivate engines in settings.yml
without commenting them out

show engine errors in infobox && add new error alert

long suggestions now wrap around the box instead of going overboard.

fix github url

[fix] fix xpath of google images

[fix] fix duckduckgo's offset

First page now starts with 0 offset,
rather than starting on the 30th result.

DuckDuckGo returns 30 results on each page.

Update translations

Add free software directory engine

[mod] the static and templates directories can be defined in the settings.yml

The exact order is
* first from SEARX_SETTINGS_PATH,
* if not found then from searx code base,
* if not found then from /etc/searx/settings.yml
* if not found an exception stops searx loading

Add Python3 compatibility