Fixes: - Correct api#sendDuelRequest arena parameter to allow null values
- Always clear "selected kit" from "history" when receiving a new kit (to avoid similar bugs in the future)
- FFA arena should also allow "/battlekit types <kit> none" kits
- Fixed ffa arena reset not working with FAWE (due to incorrectly removing them from cache)
- Fixed /arena ffa command (broke in 3.12.0)
- Fixed clickable messages functionality in newer MC versions
Improvements: - Debug log allowed random kits
- Clickable messages may now support hex (at least better than before)
- Make "enable-colored-names: false" 100% disable that code (mainly for debugging purposes)
- Migrate enderpearl cooldown from Bukkit metadata to thread-safe ConcurrentHashMap