Bug fixes + Improvements
[ + ] Added fail-safes so that when registering challenges and levels, missing data that can result in the plugin not functioning is pointed out and the challenge/level is skipped.
[ + ] Masks can now have their default duration changed, the interval at which they are checked for at, and after how many intervals the mask can reset (combats problems with effects such as health boost and nausea).
[ + ] Sellhead IDs can now be case insensitive (can be switched on and off in the config.yml)
[ + ] If an entity could not be identified when a head is dropped, a warning is logged in console (response to issue #21).
[ + ] Crafted heads no longer need sellhead IDs, and thus will not be sellable
[ + ] A notice is made when HeadsPlus hooks its PAPI placeholders
[ + ] Further progress has been made on tellraw feature