Levels Plus

This is a fork of Levels, the underlying code is almost completely different as
I abstracted most of the logic into a common package, this allows this version to be:

• Fully configurable (the cfg file now has way more entries, you can configure for instance how long "Fire" lasts or how much "Absorbs" takes, and their max levels)
• Easily implemented in other platforms (Right now supports Bukkit, Forge and Fabric)
• Possibly allow sub mods to define their own attributes and register them, thanks to a registry instead of enums
• Allow more or less than 3 levels, without being limited (eg: Soulbound in the past had 3 levels which behaved the exact same way, this has been fixed)
• Better support for displaying upgrade summary (before each level had a custom description, now it has a placeholder for the value calculated based on the level)
• Safer network implementation (old version could allow you to send fake packets and upgrade stuff without the necessary tokens and more)