[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

Add framalibre engine

framalibre.org is a catalogue of Free Software, edited by Framasoft.

For now we pass the thumbnail as img_src as it doesn't seem to be used
for IT...

Update translations

New languages: German (Germany), Finnish, Slovak, Ukrainian
Updated: Bulgarian, German, Esperanto, Italian, Japanese, Dutch,
Portuguese (Brazil), Russian, Swedish

languages.py can change, so users may query on a language that is not
on the list anymore, even if it is still recognized by a few engines.

also made no and nb the same because they seem to return the same,
though most engines will only support one or the other.

closes issue #863

Fix #872. Google search works again with docker.

All the credit goes to Wonderfall. Thanks for that!
See: https://github.com/Wonderfall/dockerfiles/issues/110

fix #850

eliminate pagination bug in search forms