[utils] Add extract_attributes for extracting html tag attributes
- use FFmpeg downloader to download m3u8 formats extracted from BrightcoveNew(some of the m3u8 media playlists use AES-128) - update comment and update_url_query to handle url query
[extractor/common] fix dash formats sorting
Pagination bug has been fixed by twitch on 15.03.2016.
[downloader/external] Add FFmpegFD
[YoutubeDL] check for --list-thumbnails immediately after processing them