Add base-denied-permissions section to standalone command manager

[onebeastchris]

No description provided.

[Konicai]

I think the main API difference I see here is that:

Before: Order of subscribers to RegisterPermissionsEvent did not matter. Additionally, default=true would always essentially be taken over default=false. I think this might've been a bad decision on my part...

Current changes: When an earlier subscriber chooses default=true or default=false, that sticks.

I think it might be nice if the caller is notified that their permission registration failed? Or should later subscribers override existing values?

Happy to help discuss :)

[onebeastchris]

@Konicai Good point. I've changed it now to allow later method callers to override the default. As for notifications - i don't think they'd be too useful, but i did add debug logging to make such cases easier to identify. Thanks for the review!