Feature added to search for youtube playlists and getting correct youtube playlist id results.
Also added duration fetching for youtube videos, which already works, but the yield self.url_result(video_id, 'Youtube', video_id, video_title) return function has still to get changed to yield self.url_result(video_id, 'Youtube', video_id, video_title, video_duration) which I did not found where to do. Otherwise it returns missmatching count of arguments.
When a YouTube playlist or channel listing has more than one page of videos, the continuation URLs specify `youtube.com` instead of `www.youtube.com`. This causes an unnecessary HTTP round-trip for each continuation page the extractor accesses.
**Example**
<code>
youtube-dl -s --print-traffic https://www.youtube.com/channel/UCBR8-60-B28hp2BmDPdntcQ
</code>
**Before**
<code>
GET /playlist?list=UUBR8-60-B28hp2BmDPdntcQ&disable_polymer=true
Host: www.youtube.com
HTTP/1.1 200 OK
GET /browse_ajax?action_continuation=1&continuation=4qmFsgIsEhpWTFVVQlI4LTYwLUIyOGhwMkJtRFBkbnRjURoOZWdaUVZEcERSMUUlM0Q%253D&disable_polymer=true
Host: youtube.com
HTTP/1.1 301 Moved Permanently
Location: https://www.youtube.com/browse_ajax?action_continuation=1&continuation=4qmFsgIsEhpWTFVVQlI4LTYwLUIyOGhwMkJtRFBkbnRjURoOZWdaUVZEcERSMUUlM0Q%253D&disable_polymer=true
GET /browse_ajax?action_continuation=1&continuation=4qmFsgIsEhpWTFVVQlI4LTYwLUIyOGhwMkJtRFBkbnRjURoOZWdaUVZEcERSMUUlM0Q%253D&disable_polymer=true
Host: www.youtube.com
HTTP/1.1 200 OK
GET /browse_ajax?action_continuation=1&continuation=4qmFsgIqEhpWTFVVQlI4LTYwLUIyOGhwMkJtRFBkbnRjURoMZWdkUVZEcERUV2RD&disable_polymer=true
Host: youtube.com
HTTP/1.1 301 Moved Permanently
Location: https://www.youtube.com/browse_ajax?action_continuation=1&continuation=4qmFsgIqEhpWTFVVQlI4LTYwLUIyOGhwMkJtRFBkbnRjURoMZWdkUVZEcERUV2RD&disable_polymer=true
GET /browse_ajax?action_continuation=1&continuation=4qmFsgIqEhpWTFVVQlI4LTYwLUIyOGhwMkJtRFBkbnRjURoMZWdkUVZEcERUV2RD&disable_polymer=true
Host: www.youtube.com
HTTP/1.1 200 OK
GET /browse_ajax?action_continuation=1&continuation=4qmFsgIqEhpWTFVVQlI4LTYwLUIyOGhwMkJtRFBkbnRjURoMZWdkUVZEcERTM2RE&disable_polymer=true
Host: youtube.com
HTTP/1.1 301 Moved Permanently
Location: https://www.youtube.com/browse_ajax?action_continuation=1&continuation=4qmFsgIqEhpWTFVVQlI4LTYwLUIyOGhwMkJtRFBkbnRjURoMZWdkUVZEcERTM2RE&disable_polymer=true
GET /browse_ajax?action_continuation=1&continuation=4qmFsgIqEhpWTFVVQlI4LTYwLUIyOGhwMkJtRFBkbnRjURoMZWdkUVZEcERTM2RE&disable_polymer=true
Host: www.youtube.com
HTTP/1.1 200 OK
</code>
**After**
<code>
GET /playlist?list=UUBR8-60-B28hp2BmDPdntcQ&disable_polymer=true
Host: www.youtube.com
HTTP/1.1 200 OK
GET /browse_ajax?action_continuation=1&continuation=4qmFsgIsEhpWTFVVQlI4LTYwLUIyOGhwMkJtRFBkbnRjURoOZWdaUVZEcERSMUUlM0Q%253D&disable_polymer=true
Host: www.youtube.com
HTTP/1.1 200 OK
GET /browse_ajax?action_continuation=1&continuation=4qmFsgIqEhpWTFVVQlI4LTYwLUIyOGhwMkJtRFBkbnRjURoMZWdkUVZEcERUV2RD&disable_polymer=true
Host: www.youtube.com
HTTP/1.1 200 OK
</code>
The old code now works again, but it downloads without limit. This is why a limit of 1000 videos is added, it can be overwritten with the `--max-downloads` option - that way, only so many ids will be extracted as videos downloaded
