Change log
- Fixed sometimes NullPointerException is thrown when player joins
- Added direction placeholders
- Added extra option to control the time of the boss bar staying on screen when hp <= 0
- Added option to control the interval between direction placeholder updates
- Added custom boss bar color&style for different damage cause
- Added WorldGuard hook to change boss bar's color&style when enter/leave region (WorldGuard and WorldGuard Events required)

***Due to config structure changes, you are strongly advised to delete the old config.yml and generate a new one. Otherwise, it might cause errors. No support will be given if using the old config file.***