Add support for cloudfront.net

[Pat38]

• Site support request (request for adding support for a new site)

The full verbose output is as follows:

> youtube-dl -v http://sites.arte.tv/28minutes/fr/michel-onfray-faut-il-interdire-les-manifestations-28minutes
[debug] System config: []
[debug] User config: []
[debug] Command-line args: [u'-v', u'http://sites.arte.tv/28minutes/fr/michel-onfray-faut-il-interdire-les-manifestations-28minutes']
[debug] Encodings: locale UTF-8, fs utf-8, out UTF-8, pref UTF-8
[debug] youtube-dl version 2016.06.20
[debug] Python version 2.7.11 - Darwin-15.5.0-x86_64-i386-64bit
[debug] exe versions: ffmpeg 3.0.2, ffprobe 3.0.2
[debug] Proxy map: {}
[arte.tv:+7] michel-onfray-faut-il-interdire-les-manifestations-28minutes: Downloading webpage
[download] Downloading playlist: None
[arte.tv:+7] playlist None: Collected 1 video ids (downloading 1 of them)
[download] Downloading video 1 of 1
[generic] mQxpgFw: Requesting header
WARNING: Falling back on generic information extractor.
[generic] mQxpgFw: Downloading webpage
[generic] mQxpgFw: Extracting information
ERROR: Unsupported URL: http://dj5ag5n6bpdxo.cloudfront.net/experience/mQxpgFw