Tag remote videos NSFW for local instance

[skid9000]

See https://github.com/Chocobozzz/PeerTube/issues/664#issuecomment-397803180

[henke37]

In short, distrust one or more followed instances and mark all of their videos as nsfw, despite what the original server says.

[skid9000]

This issue (#680) concern only specific videos on remote instances. But yeah, that's the idea.

[Nutomic]

Bumping this because I'm getting a couple of reports like this, and there is no good way to fix it (I can only blacklist the video which I don't want).

[MadMan247]

I would like to bump this issue.