Changed itemList from HashMap to ArrayList

*allows for unique instances of items
*makes weight calculation for duplicate items more cumbersome
*makes find methods slower
*but it ALLOWS FOR UNIQUE INSTANCES OF ITEMS
Make abstract subclass of Item "Equippable"

*includes a boolean "equipped" and proper accessors/mutators
	void equipSet(bool isEquipped)
	void equipItem()
	void unequipItem()
	boolean isEquipped()
	boolean equipToggle()
*Weapon and Armor classes now extend Equippable instead of Item
*Future equippable items should also extend Equippable
Merge pull request #10 from jnickg/InvItemDev

Inv item dev