Channel metadata

[Xe]

Much like the user account metadata feature request, I believe it would also be useful to have channel metadata support. Possible uses I have come up with:

• NSFW flag: disables expansion of links that a scraper marks as NSFW except for channels marked NSFW
• Link expansion flag: disables all expansion of all links at once (useful for adding Terminus-Bot to a channel that already has a link expander bot)
• ChanServ permissions flag: lets Terminus-Bot know it should use ChanServ to do all its moderation (kicking people for the roulette script, etc)

[sariyamelody]

I feel like both this and #65 should be implemented in a single module.

[Xe]

I would tend to agree, it would make things much less messy that way