Exclude all adult sites by default

[lyndalopez544]

• I'm reporting a feature request
• I've verified that I'm running youtube-dl version 2019.07.02
• [x ] I've searched the bugtracker for similar feature requests including closed ones

Description

• Move all adult site extractors to a separate folder.
• Make them not available by default and available only with something like a cli flag(e.g. --include-adult) or a boolean config

  allowAdult=true

That's the least of what that can be done.
If you want I'll do it, but I'm not so hopeful you'd accept the PR.

[dstftw]

No.

[lyndalopez544]

@dstftw Are you the project owner?
Why don't you do that?

How about at the very least making it an opt-out feature?

[dstftw]

This is useless since separating extractors is not enough for complete and reliable adult content isolation.