BETA: More OOP version of [6294].
	* All NPC should have the ability to drop items, not only those that can be attacked.
	* Avoids duplicated code.
	* Gives all NPCs the ability to drop.

git-svn-id: http://svn.l2jserver.com/branches/unstable/L2J_Server_BETA@6296 d34dfa0f-f91c-0410-86dd-cf06f19dd0ad