#31 [ENH] Exclude bots from many event triggers

e.g. another bot may post messages and do lots of edits to it later to reflect status changes or something. Lot of noise. May also lead to feedback loops with the wrong combination of bots. Keyword matchers shouldn’t react to bot messages. Things like that. Decide if it makes sense to make this a policy across the board or not. (If some other bot bans a user we probably still want to log that, so probably not 100%)