This moves playlist tests where they belong, i.e. to the extractors themselves.
Additionally, all our network interaction configuration for tests in test_download now applies to playlist tests as well.
Additional work is required to prompt the user for the SMS or phone call codes, as there is no framework currently to prompt the user during an extraction operation.
Fixes#3533
Looks like some videos are only available for particular devices
(e.g. http://player.ooyala.com/player.js?embedCode=x1b3lqZDq9y_7kMyC2Op5qo-p077tXD0
is only available for ipad)
Working around with fetching URLs for all the devices found starting with 'unknown'
until we succeed or eventually fail for each device.