Allow (approximate) plurals for eg !totaldeaths

!totaldeath is still the canonical command, and this is incomplete (not every stat can necessarily be pluralised by adding s) so undocumented... but will hopefully be useful for typos in the chat.

Having it be plural just feels more right, anyway, so understandable that people would do that.

This commit message is now 206 times longer than the actual change.
No reason this can't use the annotation pattern