handle multiple channels

[c-cube]

• [ ] need some administrative interface for trusted users, to control join/part.
• [ ] need separating state for every channel (perhaps have one instance of each plugin for each channel? Core API would multiplex)

possible issue: when talking in query with the bot, which channel's state to use?

[c-cube]

cc @reynir

[reynir]

I was just about to make an issue for this!

[c-cube]

I think it would be really cool if plugins did not have to handle this at all! Just one plugin instance per channel; the core system stores one plugin state per channel…