Ban replace logging and IRC notifications need work

[stwalkerster]

Off the back of #854 (review) ...

We probably need to refactor the set ban logic to alert differently when a ban is set to when a ban is replaced.

Ideally, I'd like a single IRC notification for when a ban is replaced mentioning both old and new ban IDs. The log entries can remain separate, but I also prefer keeping the logging calls and the IRC notification calls next to each other, even if that means a duplicated line of code