[mod] Refactor engine's search language handling

   recoll is a local search engine based on Xapian:
   http://www.lesbonscomptes.com/recoll/

   By itself recoll does not offer web or API access,
   this can be achieved using recoll-webui:
   https://github.com/koniu/recoll-webui

   As recoll-webui by default does not support paged JSON
   results it is advisable to use a patched version which does:
   https://github.com/Yetangitu/recoll-webui/tree/jsonpage
   A pull request was sent upstream, if this is merged the patched
   version is no longer needed

   This engine uses a custom 'files' result template

   set base_url to the location where recoll-webui can be reached
   set dl_prefix to a location where the file hierarchy as indexed by recoll can be reached
   set search_dir to the part of the indexed file hierarchy to be searched, use an empty string to search the entire search domain

Add match_language function in utils to match any user given
language code with a list of engine's supported languages.

Also add language_aliases dict on each engine to translate
standard language codes into the custom codes used by the engine.

Add findx engine

Add languages supported by either all default general engines or 10 engines.

[fix] Change duckduckgo url to avoid error response

Fix Vim mode on Firefox

Change alpine version to permit ARM and amd64 deployment

[UI] fix custom-select in oscar

Firefox automatically opens a built-in quick search when user
starts typing without selected input and the Vim shortcuts
are not triggered

remove the option of sourcing manage.sh

Fix Microsoft Academic engine

Fix Bing videos engine

Update README.md

ohloh is now openhub

Preserve image aspect ratio in results

Noticed that images are often distorted in the results due to a hard minimum height.  This keeps the 4-per-row image results consistent in row height without distorting wider images.

added searx-ve to gitignore

[fix] Read utf-8 files (settings, languages, currency) with Python3.5

Related to discussion in #1124
The io.open import is necessary for python2

Python3.5 is still the default Python3 version in
Debian Stretch (stable) and Ubuntu 16.04 LTS
https://packages.debian.org/source/stretch/python3-defaults
https://packages.ubuntu.com/source/xenial/python/python3-defaults

Make Python 3 able to read settings files with Unicode characters