[ShardChat] Adding features

[GabbySilver]

ShardChat is a perfectly functional plugin. It does what it's advertised to do, and it does it pretty consistently.
However it's a hint short on commands that I'd somewhat like to see, like !stop.
A command that would let us ban or !kick people would be pretty sweet as well.
Also, is it possible for the plugin to detect netsplits? There have been fewer netsplits sense espernet put some work into fixing them, but they still happen every so often.