This commit adds two new announcements for use in boss waves:
- wave-boss-killed to announce who killed the boss
- wave-boss-reward-earned to notify the killer of the boss reward, if any
Fixes#428
This makes commands case insensitive, e.g. /ma join. Note that arenas with the same name but different casing are considered the same arena, and one of them will be ignored during config-file parsing.