InventoryPanel updated to display items that are currently being held by the player. IventoryImageLoader replaces InventoryLabelImageLoader to allow easier accessing of item images.
Added item images
SinglePlayer controller pickup and drop logic implemented.
Lever room drop and pick up items implemented.
Method signature changes (ItemNode to BasicNode) + Library imports.
Room removeItem() fixed
Merge branch 'develop' of https://github.com/mrwinton/TheExcellentAdventure into develop

Conflicts:
	src/client/Client.java
	src/controllers/Controller.java
	src/gameworld/items/ItemManagerImpl.java
	src/main/Main.java
	src/ui/GameFrame.java
	src/ui/InventoryPanel.java