Add module toggles

[xemlock]

Currently toggling modules is not granular enough - there is only one switch (HTML.Trusted) which enables all unsafe modules. And there is no way of enabling Forms module without also enabling Scripting. You can do something like the following, but it's not convenient and seems like a dirty override:

$config = new HTMLPurifier_HTML5Config::create([
    'HTML.Trusted' => true,
    'HTML.ForbiddenElements' => ['script', 'noscript'],
]);

Related to ezyang/htmlpurifier#213.

[bytestream]

It's cumbersome but you can do this using HTML.AllowedModules. List all the modules you want to allow and any not listed will be removed.

[xemlock]

Closing, as %HTML.Forms config flag is sufficient for now.