update bing engines and fix bing_news
add bing_images
add comments to google-engines
fix dailymotion engine and add comments to it
fix yahoo engines and add comments
fix vimeo engine and add comments

engine generate (Error: None), I don't know why
Merge pull request #88 from pointhi/engines

update and fix search engines
add comments to deviantart engine
little refactoring
rewrite duckduckgo engine and add comments
add comments to dummy engine
update generalfile engine and add comments
update github engine and add comments
update piratebay engine and add comments
update soundcloud and add comments
add little comment
fix stackoverflow and add comments
fix startpage engine and add comments

* add language support
* remove not required code
* improve google-ad detection (no false detection anymore, I hope)
* other improvements
fix twitter engine and add comments

* add language-support
* add comments
* little refactoring
remove categories : social media from twitter engine in settings.yml