Re-introducing the chance overflow of old L2J drops.

Simplier way than recoding everything to re-introduce chance overflow without killing the drop system behavior.

I think this is the mostly missing piece.

I've talked with @NosBit about it and he said that way is fine.

This has been in production for the past 6 month without any issues, and feedback from players is more than convincing to say it's pretty much the same as it was.

Just hope I didn't introduce any mistake adding config (it was hardcoded in my fork :)
It has a meaning in #1 but here one item is enough but it is better to use Collections#singletonList() or Arrays#asList() instead