Results 2 issues of pydis-bot

Some errors use plain messages (e.g. general error handlers and moderation cogs) while others use embeds, sometimes even including [humorous replies](https://github.com/python-discord/bot/blob/master/bot/constants.py#L585) (e.g. reminders and clean cogs). Errors don't necessarily refer...

t: feature
a: frontend
p: 3 - low

**Originally posted by Leon Sandøy:** The bulk delete event is ignored in mod-log, but both Clean and AntiSpam need to do bulk deletes. There should be a single, consistent way...

t: feature
a: backend
s: stale
p: 3 - low