Initialize object on page
	
	
			
	
		Parameters passed to the constructor are:
			object to attach tree to (should be loaded before calling constructor)
			width of the tree
			height of the tree
			identifier of level parent to tree root level
		Specify Additional parameters of the tree:
			setImagePath(url) - method specifies the path to the folder with tree icons
			loadXML("tree.xml") - load tree items from XML