Counts the number of things you've killed, keeps totals by level, as well as breaking out how many you've killed this session.

This is designed to be a very simple addon, with a minimal command line UI, and simple tooltip based output.

(This has no doubt been done several times, probably better, by other people, but here's my version anyway.)

Kills are'yours' if either:

* You get XP for them
* You have the victim targetted and it dies after you've inflicted some damage on it (This will likely not play well with target-flipping addons, but only matters if you care how many things that dont yield XP you've killed)