Configurable Despawn Timer

The big 4.0 update!
Support has been added for experience orbs, alongside items.
There is now a config option, disabled by default, to never despawn player-dropped items.
A config file is generated containing each item, where specific despawn times can be set.
There is a reload command for this config file.
Fixed the /give command dropping a duplicated item.
Updated the mod icon.

The complete changelog with previous versions can be found at:
  https://serilum.com/mods?changelog=configurable-despawn-timer