Close issues about '@handle' URLs not working

[tcely]

After #640, we should now have support for adding these channels without the user converting them to a channel ID for the software.

This is a collection of open issues about adding those channels:

• channel 404 with /c/ in the url #481
• youtube.com/c/ No Longer Valid?? #461
• No metadata was returned by youtube-dl #393
• How to deal with @ in channel name? #299
• YouTube handles #277
• Add sources with /user/ URL #243
• Add YouTube Channel by ID without requiring full URL #234
• Invalid URL, the URL must for a "YouTube channel"  #160
• This source has encountered permanent failures listed at the bottom of this page, check its settings #114
• Old user channel format not supported #82

[meeb]

Yep fine with me. I'll go through these when I get a moment. Thanks for looking them up.

[tcely]

They all appear closed now. Thanks.