ArteTVIE: extract the video with the correct language

Some urls from the French version of the page could download the German version.

Also instead of extracting the json url from the webpage, build it to skip the download
[auengine] Add tests (Fixes #985)
Merge branch 'master' of github.com:rg3/youtube-dl
[arte] Fix language selection (Fixes #988)
release 2013.07.04