Refined the reference/element system.
Retired some ItemUtil methods, replaced some with new ones.
ItemUtil still needs some finishing for all updating methods.

Added new class:
 - ElementsUtil for getting any element using a reference

Added new .yml files:
 - drops.yml for setting special drops for mobs with names
 - itemtypes.yml for setting elements for each item reference
 - names.yml for all the names of references
 - spawnnodes.yml since I forgot that earlier