Passive Skill Trees

New features:

- Added item modifiers that grand bonuses

- Added special workbench block

- Added two types of unlockable recipes for the workbench

- Added skill bonus that allows players to add more item modifiers to items

Minor changes:

- Reduced size of some skill data files

Comment:

 This update mostly adds features that are going to be later used by some classes. I'm releasing it early to let modpack developers experiment with these features.