Included support for the PlayerDamageItemEvent.

- updated to 1.20
- implemented a developer api (TreeFellerAPI.java)
- implemented a TreeFellerEvent (usage is just like a regular Bukkit event)

- Added a list for tree blocks

Added Config option to check if player is sneaking

- ToolDamage is now toggleable

- Fixed api-version, nether is now supported again!

- Added Config to edit maxTreeSize and maxTreeHeight
- Improved performance

- Checks if a broken tree-block is a tree
- Better performance on larger trees

- Added type "wood"
- Added type "stem"
- Added type "hyphae"

- Fixed tools normal damage