ddg encoding of URLs to UTF-8

Add Image on opensearch

some Bug fixes

Seeing on the official instance, searching with non-ascii character
usually renders mojibake non-sense:

    http://searx.me/?q=%E9%A3%9F%E5%A0%82&categories=files

Screenshot with broken: ![](https://imgrush.com/1NNr_Rpv-rt2.png)

Screenshot of the fixed rendering: ![](https://imgrush.com/khe4M2P3VAyq.png)

[fix] Piratebay engine

Add portuguese translation

[fix] reduce server traffic by optimizing images

update dependency versions described by versions.cfg

Simply running ‘optipng’ on every PNG image reduces the overall size of
them by 10% on average.

Conflicts:
	searx/plugins/__init__.py

- regexes in a array
- regexes applied only on the last part of the url

Add a self user agent plugin

Fix vimeo

Just like with the "ip" query, duckduckgo gives the server's
information with the "user agent" query.
This corrects this behavior by adding a plugin based on self_ip.py plugin.

Update Dockerfile.

- Install new packages needed to deploy search
- Optimize dockerfile for more docker deamon caching
- Pin a python2.7 base image.