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
Implement format selection in YoutubeDL

Now the IEs can set a formats field in the info_dict, with the formats ordered from worst to best quality. It's a list of dicts with the following fields:
* Mandatory: url and ext
* Optional: format and format_id

The format_id is used for choosing which formats have to be downloaded.

Implemented in TEDIE.
ArteTV: implement multiple formats