#33 [ENH] Exclude certain channels and/or users from events

Loose idea, but have the ability to exclude certain channels or users or user types from certain kinds of events, perhaps globally. Use cases: - Other bots posting messages that then lead to log events in Rocketbot - A channel where automated posts are generated leading to events in Rocketbot - Mods typing filtered words - Certain privileged users typing filtered words Perhaps add a centralized function to BaseCog for easily doing boilerplate exclusions. May need different kinds of boilerplate exclusions, depending on what the cog is looking for. Maybe have 2-3 types. Use cases: - Ordinary member posting a filtered word (proceed with event) - Mod posting a filtered word (ignore event) - Mod reacting to a bot message to trigger an action (proceed) - Bot doing almost anything (ignore) - Event triggered by Rocketbot itself (ignore) - Mods commenting in a mod channel (possibly ignore for privacy reasons) Some rules can be baked in but others should be configurable. Think about what that division might look like and what simple-but-powerful configuration might make sense.