- Changed the fortune and looting effects to better mimic the vanilla behaviour.

A more detailed explanation on the new modifiers:

- Multiplicative modifier: Repeats the drop attempt once per enchantment level with the drop chance of the drop times the modifier minus 1.
For example: If the modifier is set to x1.5, killing a mob with looting 2 will attempt twice to drop the item with a (0.5 * item drop chance) chance of succeeding each time. (This is the recommended modifier type).

- Additive modifier: Repeats the drop attempt once per enchantment level with the drop chance of the modifier.
For example: If the modifier is set to +10%, killing a mob with looting 2 will attempt twice to drop the item with a 10% chance of succeeding each time.