[twitch] Adapt to new API (Fixes #3946, Fixes #3949, Fixes #3965)

 Work in progress
[vimeo] Improve regex for the config js dict (fixes #3955, fixes #3974)

The javascript code contains assignments of empty dicts with the same variable name
[twitch] Rename extractor and support channel videos
[twitch] Update tests and minor improvements
[generic] Make sure Wistia embed URLs contain the protocol (Closes #3977)

Also, improve detection (Addresses #3662)
[arte.tv:+7] Append media type to format_id (Closes #3967)